WO2002095810A1

WO2002095810A1 - Method of repairing molecular electronic defects

Info

Publication number: WO2002095810A1
Application number: PCT/US2002/016321
Authority: WO
Inventors: Thomas E. Mallouk; David L. Allara; David M. Kaschak
Original assignee: Molecular Electronics Corporation
Priority date: 2001-05-21
Filing date: 2002-05-21
Publication date: 2002-11-28

Abstract

Methods of repairing or preventing defects in molecular electronic devices encompassing optical, alternate logic, and molecular memory devices by way of electropolymerization of insulating polymers, surface-catalyzed polymerization of insulating materials, and surface sol-gel filling of voids.

Description

METHOD OF REPAIRING MOLECULAR ELECTRONIC DEFECTS

This application claims the benefit of Provisional Patent Application, Serial

No. 60/292,749, filed May 21, 2001, entitled "METHOD OF REPAIRING

MOLECULAR ELECTRONIC DEFECTS".

FIELD OF THE INVENTION

The invention relates generally to molecular electronic devices encompassing

optical, alternate logic, and molecular memory devices and, more particularly, to

methods for repairing or preventing defects in such devices.

BACKGROUND OF THE INVENTION

The need for alternate logic and memory devices for miniaturization, faster

speeds, longer refresh times, lower cost, alternate substrate platforms, etc. is opening

a newly emerging industry described as molecular electronics. Those skilled in the

art delve far below the sub-micrometer scale regime to demonstrate miniaturization,

elucidate fundamental theories, or test new hypotheses. While miniaturization

presents many challenges, it also offers many benefits. One of the benefits is that the

number of defects in the actual molecular electronic device becomes statistically

reduced as the device area becomes smaller.

Molecular electronic devices usually contain very thin films of organic or

inorganic molecular or polymeric materials sandwiched between metallic

conductors. Unfortunately, single defects in such films can create short circuits or electron tunneling pathways that can seriously impair the function of a circuit that

contains a molecular electronic device. As a prelude to the large-scale manufacture

of single molecule- and polymer-based electronic devices, it is important to provide

a fabrication method that is rapid and cost effective. Initially, this technology may

not be done at the cutting edge of area miniaturization with regard to memory or

logic density platforms due to the nature of market insertion for this type of

technology. To accomplish early feasibility demonstrations, memory or logic cell

areas approaching square micrometers must be demonstrated reliably. This and the

requirement that later generations of smaller area molecular electronic devices will

have to be made with high yields gives rise to the need for a process that eliminates,

prevents, or fixes film defects at the molecular level.

A molecular memory or logic device incorporates molecules or polymers that

display high and low conductivity states, current rectification, resistance,

capacitance, or other useful electronic properties when properly arranged on a metal

or other conductive substrates or between two such surfaces. Preferred examples of

metal substrates are those typically used in electronics, including copper, gold,

silver, palladium, platinum, and aluminum. Preferred examples of non-metallic

conductive substrates include doped semiconductors (n-type or p-type silicon,

polysilicon, amorphous silicon, gallium arsenide, gallium arsenide phosphide,

germanium) and conducting polymers (such as poly(pyrrole), poly(aniline), and

poly(thiophene)). One example of the molecular component of these devices is a molecule

exhibiting negative differential resistance (NDR). Preferred examples in this class of

molecules include oligophenyleneethynylene derivatives (J. Chen, M.A. Reed,

A.M. Rawlett, J.M. Tour, Science 1999, 286, 1550), viologens (C.P. Collier, E.W. Wong;

M. Belohradsky, F.M. Raymo, J.F. Stoddart, P.J. Kuekes, R.S. Williams, J.R. Heath,

Science, 1999, 285, 391), metallocenes, metalloporphyrins, and metallopthalocyanines.

Others examples of NDR molecules are molecules that include transistor

functionality (J. Schon, H. Meng, Z. Bao, Nature, 2001, 413, 713), diode behavior

(R.M. Metzger, B. Chen, U. Hopfner, M. Lakshmikantham, D. Vuillaume, T. Kawai,

X. Wu, H. Tachibana, T. Hughes, H. Sakurai, J. Baldwin, C. Hosch, M. Cava,

L. Breh er, G. Ashwell, /. Amer. Chem. Soc, 1997, 119, 10455), resistance, capacitance,

etc. depending on the molecular structure. Still others are conducting polymers,

such as those mentioned above, which have been previously shown to have

switching, rectifying, or transistor-like behavior (G. P. Kittlesen, H.S. White,

M.S. Wrighton, /. Am. Chem. Soc. 1985, 107, 7373).

Molecular memory and logic devices incorporating palladium, platinum, and

aluminum molecules or polymers that display high and low conductivity states,

current rectification, resistance, capacitance, or other useful electronic properties

have the distinct advantage over conventional semiconductor-based devices in that

their functionality does not change as the device area and thickness are scaled down,

even to the single molecule level. In contrast to molecular memory and logic

devices, current solid-state memory and logic devices suffer from quantum effects at the extreme limits of miniaturization. A further advantage of molecular memory

and logic devices is that changing device characteristics does not require

prohibitively expensive process changes; instead, the choice of device functionality is

accomplished by altering the structure of the molecule used as the memory or

logic element.

SUMMARY OF THE INVENTION

The present invention comprises alternative methods for filling, repairing, or

preventing voids and defects in a molecular layer between about 0.30 and about 100

nanometers in thickness (in the class of chemically bonded or attached

(chemisorbed) or physically adsorbed (physisorbed), hereafter collectively

"adsorbed" organic molecules) for the purposes of avoiding short circuits, repairing

defects between electrical contacts, decreasing leakage currents, increasing device

and circuit lifetimes, and increasing yields in device fabrication for memory and

logic applications. These voids and defects most commonly consist of localized

areas of the molecular layer in which there is incomplete coverage of the conductive

substrate by the molecular layer most commonly manifested as pinholes in the

surface, or boundary regions where individual domains of well-ordered molecular

layers meet each other, or where the underlying substrate contains ordered atomic

domains meet each other (collectively referred to as grain boundaries. At these

boundary regions, the organic layer is typically thinner than it is in well ordered

regions and, hence, it is more likely that a short circuit will be formed between the top and bottom conductive contacts, whether the top contact is applied by solution-

or gas-phase methods.

The molecular layers may be self-assembled monolayers ("SAMs") and other

physisorbed organic layers (including aliphatic and aromatic monolayer-forming

molecules that contain terminal thiol, disulfide, carboxylate, isonitrile, amine,

hydroxamate, phosphate, phosphonate, alkoxysilane, or halosilane groups, or other

molecules such as free radicals or aryl halides that can be covalently coupled to the

surfaces of conductors), thicker organic films made by adsorption of polymers

(including the conducting polymers listed above (poly(pyrrole), poly(aniline), and

poly(thiophene)), and semiconducting polymers (such as poly(phenylenevinylene)

and poly(diacetylenes), inorganic molecular films (such as metal phosphonates,

metal-cyanide networks, metallocenes, metalloporphyrins, and

metallopthalocyanines), inorganic nanoparticle films (in particular metal or carbon

nanoparticles, particles of semiconducting oxides such as ΗO2, ZnO, or Sn0₂,

particles of 13-15 semiconductors including GaAs and InP, and particles of metal

chalcogenides such as CdSe, CdTe, MoS_2/ and WS₂), or multilayers of molecules

(such as aromatic molecules or macrocyclic compounds) deposited from solutions or

from the vapor phase onto electronically conductive surfaces. The inventive

methods include, as treatment of the surface of the molecular layer,

electropolymerization of insulating polymers, surface-catalyzed polymerization of

insulating materials, and surface sol-gel filling of voids. Electropolymerization of insulating polymers

Molecules have been electro-oxidized or electro-reduced in the past in bulk

electrochemical oxidations or reductions using macroscopic planar electrodes.

General classes of such molecules most commonly include hydroxyl phenyl alcohols

(to form polyphenylene oxides), vinyl benzenes, N-alkyl pyridinium salts, and

vinyl pyridines.

Electropolymerization of insulating polymers in the current invention, in

contrast, is directed to insulating electronically conductive substrate voids and

defects in a self-assembled or other physisorbed molecular monolayers. In

accordance with this method, a soluble molecule is electrochemically oxidized or

reduced to a polymeric form onto or into the voids or defects by dissolving the

soluble molecule in an electrolyte solution, immersing the electronically conductive

substrate in the solution, and applying an appropriate potential to electropolymerize

the molecule. The application of the potential will be terminated when the desired

degree of filling, etc. is achieved. In one embodiment, this will be when the current

attributed to the oxidation or reduction of the soluble molecule falls to 2% or less of

its peak value. In another, the current will be at 0.1% or less of its peak value.

Such electropolymerization of insulating polymers covers defects in these thin

molecular layers that would otherwise lead to device short circuits or electron

tunneling pathways. The thin layers of interest in molecular electronic devices

include self-assembled and other physisorbed organic monolayers (typically about

0.5 to about 4.0 nanometers in thickness, and most preferably between about 0.7 and about 3.0 nanometers), adsorbed organic polymer layers (typically between about 0.5

and 50.0 nanometers in thickness), crystalline or amorphous films of monomeric

organic molecules (typically from about 0.3 to about 100.0 nanometers in thickness),

or films of inorganic particles that are between about 1.5 and 100.0 nanometers in

thickness. The conditions of the oxidation or reduction must be compatible with the

chemical properties of the thin layer that comprises the molecular electronic device

and this is where the prior art falls short of achieving the intended goal with the

molecular layers of interest in the practice of the present invention. For example,

attempts to coat pinholes in octadecanethiol monolayers on a metal substrate by

electropolymerization of phenol have been found to oxidatively break the metal-

thiol bond, thereby increasing rather than decreasing the density of defects in the

device molecule monolayer. In some cases, the thiol-bound NDR molecules were

completely stripped from the metal surface using this approach.

A window of useful electrochemical potentials (relative to the SCE reference

electrode) has been discovered in accordance with the present invention to maintain

the integrity of a functional NDR monolayer (or other electronically active organic

layer, as in the case of switching, rectifying, resistive, transistor-like, or other

electronic device functions), while electrochemically oxidizing or reducing the

insulator within the pinholes in the monolayer to prevent short circuits or electron

tunneling.

1, 2-Diaminobenzene and structurally related aromatic amines (specifically,

aniline and aminonaphthalene derivatives, and preferentially aromatic amines in which the aromatic ring contains at least one other electron-donating group such as

amino, hydroxy, or alkoxy) can be electrochemically oxidized within the pinholes of

a molecular monolayer in accordance with the present invention. While

1, 2-diaminobenzene in particular is known to have a surface reaction and to be

useful for improving the performance of metal chalcogenide electrodes by reducing

surface imperfections, 1, 2-diaminobenzene and structurally related aromatic amines

(specifically, aniline and aminonaphthalene derivatives, and preferentially aromatic

amines in which the aromatic ring contains at least one other electron-donating

group such as amino, hydroxy, or alkoxy) have not been used on metal substrates, in

processes relevant to molecular memory or logic devices, or in any applications

seeking to reduce the total number of molecular layer defects or to solve relevant

processing problems for molecular memory or logic fabrication.

1, 2-Diaminobenzene and structurally related aromatic amines (specifically,

aniline and aminonaphthalene derivatives, and preferentially aromatic amines in

which the aromatic ring contains at least one other electron-donating group such as

amino, hydroxy, or alkoxy) are useful polymer precursors in this application because

they are easily electro-oxidized. Therefore, they can be polymerized at potentials

that do not damage the molecular layer. Because thiol SAMs are oxidatively

desorbed from gold surfaces at positive potentials, beginning at about +0.8 V vs.

SCE, preferred polymer precursors are oxidized at potentials lower than or equal to

about +0.6 V vs. SCE. If other metal/SAM combinations are used (for example,

isonitrile SAMs on Pd or Pt, or covalently linked alkyl or aryl SAMs on silicon), the preferred potential for the electropolymerization will vary depending on the

potential range in which damage to the SAM occurs.

Electro-oxidation forms a cross-linked polymer that is very insoluble in

common electrochemical solvents, such as water, alcohols, acetonitrile,

dimethylformamide, and dichloromethane. The polar amino groups also promote

polymer adsorption to hydrophilic electronically conductive surfaces. Other

preferred polymer precursors include aromatic amines, aromatic alcohols, N-alkyl

pyridium salts, vinylbenzenes, and vinylpyridines. In principle, any polymerization

reaction that can be initiated electrochemically at a potential that is compatible with

the molecular layer can be used. These include free radical polymerizations as well

as polymerization reactions initiated by electrochemically generated acids or bases.

Useful variations exist including depositing and curing deposited polymer (e.g.,

amine + epoxy functionality).

Alternate electrochemical processes can be utilized in order to insulate defect

sites or to prime them for adsorption of insulating films. One such technique is

underpotential deposition (UPD). UPD is an electrochemical technique for growing

a self-limiting thin film of a metal or metal oxide on a different metal, and can be

used to prime defect sites for growth or adhesion of an insulating layer (see

E. Herrero, L.J. Buller, and H.D. Abruna, Chemical Reviews, 101, 1897-1930 (2001)).

For example, if the metals or metal oxides are deposited in this way, the

underpotentially deposited material can act as a hydrophilic attachment site for

other insulating (or less conductive) materials. A UPD layer of copper on Au can be used to enhance the adhesion of molecules containing phosphonate groups, such as

1, 10-decanediylbis (phosphonic acid). The phosphonate group attached in this way

can be used to nucleate the growth of insulating metal phosphonate films as

described by G. Cao, H.-G. Hong, and T.E. Mallouk, "Layered Metal Phosphates and

Phosphonates: From Crystals to Monolayers," Accounts of Chemical Research, 25,

420-427 (1992).

Another alternative electrochemical technique is polarization of the SAM-

covered working electrode. In this approach, an NDR self-assembled monolayer is

first adsorbed to a gold surface. The adsorption is accomplished by soaking the gold

substrate in a solution containing the NDR molecule, which contains a terminal thiol

group that binds to the surface. Then, the coated substrate is immersed in an

aqueous electrolyte solution and a current is applied with a sufficiently negative

potential so that hydrogen is evolved from the contacting aqueous electrolyte

solution. Depletion of hydrogen ions in the vicinity of the metal surface causes a

local increase in pH and the local precipitation of insulating polymers or metal

oxides. Insulated metal oxides that can be deposited in this way are those that

derive from metal ions that are soluble at low pH (including Fe³⁺, Fe²⁺, Al³⁺, Zr^4"1",

Co²⁺, Ni²⁺, and Zn²⁺) and form insoluble oxides or hydroxides at higher pH.

Polymers that can be deposited in this way include poly(amines), such as

poly(ethyleneimine) and poly(aniline), which have greater solubility in acidic than in

basic aqueous solutions. Finally, in addition to insulating defects in thin molecular electronic layers,

the present method can be used as a diagnostic of film quality, since the

electropolymerized deposits are typically thicker than the self-assembled monolayer

or physisorbed molecular film. Thus, these deposits can be imaged by techniques

such as atomic force microscopy (AFM) to reveal which regions of a thin film coated

on a metal substrate are high or low in defects.

The present invention will now be illustrated by the following examples,

however, it should be understood that the invention is not meant to be limited by

the details therein.

Example 1

In a typical example, a 1-10 millimolar solution of 1, 2-diaminobenzene is

made in acetonitrile solvent by mixing the compound with the solvent at ambient

temperature, and adding a sufficient quantity of an electrolyte salt such as

tetra(n-butylammonium) perchlorate to make a 0.1 M solution. A [gold?] metal

substrate coated with a SAM of molecule I is immersed in this:

I (Ac = CHsCO)

solution and used as the working electrode of a standard three-electrode

electrochemical cell, which also contains a platinum auxiliary electrode and a

saturated calomel electrode (SCE) as a reference. The electrode is cycled at 50 mV per second between 0.0 and +0.6 V vs. SCE for 10-20 cycles; alternatively, the

electrode is held steady at +0.6 V for a period of 5-10 min. This potential is chosen to

be sufficiently positive to oxidatively polymerize the 1, 2-diaminobenzene at

exposed areas of the working electrode. However, the potential must not be positive

enough to cause oxidative desorption or decomposition of the SAM layer. The

number of cycles or the holding time at the positive potential are determined by

observing the current, which decreases with progressive cycling or with increasing

time as the defects in the monolayer are covered. The process is stopped when the

anodic current attributed to oxidation of 1, 2-diaminobenzene fell to 0.1% of its peak

value in the first cyclic voltammetric sweep anodic half -cycle of the process.

The working electrode is then returned to 0.0 V and removed from the

solution, rinsed twice with acetonitrile, and dried in a stream of inert gas, such as

nitrogen or argon. When examined by cyclic voltammetry in an aqueous solution

containing 1 mM K Fe(CN)₆, it can be seen that the oxidation-reduction current

normally attributed to grain boundary defects or pinholes in the monolayer is

significantly suppressed. The electrochemically generated polymer is preferentially

formed in areas where the metal is exposed to the solution and adsorbs in such a

way as to cover the exposed metal surface. The process is self-limiting because the

electropolymerization reaction slows down or stops when the exposed metal area

is covered. Example 2

In this example, electropolymerization is used to repair monolayer pinholes,

in an NDR self-assembled monolayer such as a SAM of molecule I. First, a related

oligophenyleneethynylene is adsorbed to a gold surface. The adsorption is

accomplished by soaking the gold substrate in a solution containing the NDR

molecule, which contains a terminal thiol group that binds to the surface. Next, a

molecular precursor to an insulating polymer layer (in this case

1, 2-diaminobenzene, or a different aromatic amine or alcohol that can be oxidized at

a potential lower than 0.8 V vs. SCE) is electro-oxidized onto the surface. The

precursor is chosen to give a polymer that covers or fills the defect site by virtue of

its insolubility in the electrolyte solution and/ or its strong adsorption to the exposed

metal at the defect site. The precursor is preferably a molecule, such as an easily

oxidized aromatic amine or phenol derivative, that forms a cross-linked polymer

when oxidized. The electro-oxidation occurs only at the surface sites available for

solution electrochemistry. These sites are the defects in the SAM, because the non-

defective areas are electronically insulating.

Example 3

The efficacy of the procedure of Example 2 above is illustrated on

macroscopic bare and SAM-coated gold electrodes in Figure 1 (top graph). As seen

in Figure 1 (top graph), as the working electrode potential is progressively cycled at

50 mV per second between 0.0 and +0.6 V, defects in the monolayer are covered by the insulating cross-linked polymer formed in the oxidative electrode reaction of

1, 2-dιammobenzene Alternatively, the potential of the electrode can held for

several minutes at the positive potential limit, +0 6 V

Figure 1. 1,2-diaminobenzerte oxidation

Potential (V vs SCE) Consequently, the area available for additional electropolymerization decreases in

successive cycles.

Example 4

Figure 1 (bottom graph) compares blockage of Faradaic current from

I Fe(CN)₆ in an electrolyte solution on a bare planar gold electrode, an identical

electrode modified with a SAM of NDR molecule I, and the same electrode modified

with both a SAM of I and electro-oxidized 1, 2-diaminobenzene. Dramatically

decreased currents are observed with both the SAM and electropolymerized

insulator present showing that the current path to the solution is effectively blocked

by the SAM in areas where it is non-defective, and by the polymer in areas where

defects were covered.

Example 5

Amine functionality can be introduced at defects in the molecular or

polymeric layer on the electrode surface by electropolymerizing an aniline or

diaminobenzene derivative as described above. Then a 1-10 mM solution of

molecules containing two or more epoxy groups (as are commonly used in epoxy

adhesives) in acetonitrile or dichloromethane can be added to cross-link the

polymer. These epoxy cross-linkers preferentially bind to the amine groups, which

are present primarily at the defect sites. After an appropriate reaction time (typically

1-2 hours at a temperature between 23°C and 50°C) the electrode is removed from the solution and rinsed several times with acetonitrile or dichloromethane to remove

unbound epoxy cross-linker molecules.

Surface-catalyzed polymerization of insulating materials

Non-electrochemical methods for polymerizing very thin films on metal

substrates can involve spontaneous surface-catalyzed reactions. Prior art techniques

include the formation of polymethylene at bare gold surfaces, with initiation at

defect sites and grain boundaries. These techniques are aimed at creating controlled

area electrodes with nanometer scale pores that allow rapid diffusion of solution

species to the electrode surface.

In the surface-catalyzed polymerization of insulating materials of the present

invention, polymethylene is surface-catalyzed after a thin organic layer, such as a

SAM or adsorbed polymer film, has been deposited onto a metal surface, as

described above. Defects and voids in the thin film structure allow access of

diazomethane which is introduced from the gas or solution phase, to the catalytic

metal surface, thereby nucleating the growth of polymethylene only where defects or

voids in the film are present. This, in turn, results in a sealed surface, free (or nearly

free) from pinholes and defects in the layer. Again, additional differences from the

prior art include the formation of polymethylene or other surface-catalyzed

polymerization reactions at defect sites under conditions that are compatible with

molecular device manufacture. The deposition of the polymethylene must be done at

a temperature below about 250°C in order to avoid pyrolysis or desorption of the molecular device layer. Other compounds that could be used include any derivative

of diazomethane such as fluorinated or alkyl-containing derivatives of

diazomethane. Also, molecules that are catalytically polymerized on contact with a

metal surface could be used. Most preferably, the molecule is introduced from the

gas phase and the polymer that results is insoluble.

Surface Sol-gel filling of voids

Techniques for making high dielectric thin films of tunable thickness at the

surface of inorganic oxide or organic hydroxyl functionalized substrates are known.

These inorganic oxide or organic hydroxyl functionalized substrates are typically

composed of oxides of Ti, Ta or mixed compositions thereof. The general technique

termed Surface Sol-Gel synthesis (SSG) has been utilized to make thin films of CdS,

ZnS; Ti, Zr, Nb, Ta, Si, Al, B, Zn, and Mn oxides. SSG involves a series of chemical

processing steps in which a soluble molecular inorganic compound is chemically

adsorbed on a surface, typically from a non-aqueous solution, and then reacted with

a second compound (such as water or hydrogen sulfide) to make a monolayer

coating of an insoluble inorganic material. These steps are repeated to grow the

inorganic material in layer-by-layer fashion. The technique is generally useful for

making patterned surface structures due to the selective layer-by-layer growth of

material onto, for example, hydroxyl functionalized surface groups.

In the present invention, SSG is used in an entirely new way to fill the voids

in an electronically active monolayer of a molecular electronic device with an insulating material to achieve decreased leakage currents, increased device yields

and longer device performance lifetimes. The materials that can be used in the

present method include the aforementioned sulfides and oxides, sulfide, fluorides,

nitrides, and oxynitrides of transition metals and post-transition elements, as well as

oxides, sulfides, fluorides, nitrides, and oxynitrides of the lanthanides (the fourteen

elements from La to Lu in the periodic table). Preferred oxides include silicon oxide,

tantalum oxide, zirconium oxide, hafnium oxide, and aluminum oxide. Alternative

methods include those used to make nitrides, fluorides, oxynitrides, for example, by

employing ammonia or hydrogen fluoride in place of the water or hydrogen sulfide

used in the current SSG technique.

Molecule Exchanges to Fill Defects

Defects in thin molecular films may also be accomplished in accordance with

the invention by way of small or large molecule exchanges, in which an insulating

molecule fills voids or replaces an electronically active molecule. This can be done

via warm/ hot solvent exchange, vapor phase exchange, and surface annealing

reactions that serve to introduce additional molecules into an adsorbed molecular

film. In general, these are molecules that contain a surface ligating group, such as a

thiol in the case of a gold substrate. The balance of the molecule is an insulating

group, such as a polymethylene chain. Preferred examples in the case of gold

surfaces are octadecanethiol, which is introduced by a solution exchange reaction,

and hexanethiol, which is introduced from the vapor phase. These exchanges of an insulating molecule for an electronically active one, or surface adsorption processes

at defects or grain boundaries, can be utilized in a process suitable for maintaining

the integrity and functionality of the molecular memory or logic thin layer. Again,

these are conditions of temperature, solvent, and/ or electrode potential that do not

result in the desorption or decomposition of the electronically active organic layer.

Monolayer exchange may be utilized, for example, to fill voids in the device

layer as follows. A molecule that forms a crystalline self-assembled monolayer, such

as a long-chain alkane thiol CH₃(CH2)nSH, n > 5, can be introduced into a monolayer

of NDR molecules by exposing the SAM-covered substrate to a solution or vapor

containing this molecule. Alternatively, exchange reactions can also be used to form

useful top functionalized molecules, thereby increasing the number of possible post-

deposition chemical reactions that can be used to "cap" the top of the molecular

layer. The capping can be done either by the surface sol-gel process described above

or by adding using the new functional group as a point of attachment for the top

metal layer deposition. In the latter case, the evaporated top metal is coordinated by

the functional group at the top of the organic layer, preventing penetration of the

film by metal atoms. Examples include SAM-forming molecules (thiols, thioacetates,

isonitriles, etc.) that contain terminal halogen atoms, such as XCH(CH₂)_nSH, where

n > 5 and X = I, Br. The terminal group can act as point of oxidative displacement

reactions with metals (in the case of an iodo- or bromo-terminated molecule). In this

reaction attached molecules on a metal surface (M_SUrf)-S(CH₂)_nX react with vapor

phase metal atoms (M') to nucleate the growth a top metallized structure that can be represented as (M_Surf)-S(CH₂)_n(M')mX, where (M')_m is a single or multiple layer of

metal atoms. Another approach is to use carbonyl-containing terminal groups such

as COOH or hydroxamate, or another ligating group such as an amine, alcohol,

silanol, phosphate, or phosphonate, to either act as a point of attachment for an

inorganic oxide grown by the surface sol-gel method, or to function as an attachment

site for organic esters, silanes, etc. For example, a surface (M_SUrf)-S(CH₂)nCOOH can

be reacted with a metal-organic molecule M'(OR)_n, where M'(OR)_n is a sol-gel

precursor such as tantalum ethoxide or titanium isopropoxide, or more generally

with any soluble metal-organic that is hydrolyzed in water. The surface attachment

is in this case of the form (M_SUrf)-S(CH2)nCOOM'(OR)_n-ι, and the bound metal

organic complex nucleates the growth of the surface sol-gel film. Similar reactions

can be written for the other ligating groups specified above.

While the present invention is described above in connection with preferred

or illustrative embodiments, these embodiments are not intended to be exhaustive or

limiting of the invention. Rather, the invention is intended to cover all alternatives,

modifications and equivalents included within its spirit and scope, as defined by the

appended claims.

Claims

CLAIMSWhat we claim is:

1. An electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer between about 0.30 and about 100 nanometers in

thickness adsorbed on an electronically conductive substrate comprising:

electrochemically oxidizing or reducing a soluble molecule, the soluble

molecule comprising a polymer precursor to a polymeric form, by dissolving the

soluble molecule in an electrolyte solution, immersing the conductive substrate

bearing the molecular layer in the solution, and applying an appropriate potential to

electropolymerize the molecule, where the potential is at a level less than that which

would cause oxidative desorption or decomposition of the molecular layer; and

terminating the application of the potential when the current attributed to the

oxidation or reduction of the soluble molecule falls to 2% or less of its peak value.

2. The electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer adsorbed on a conductive substrate of claim 1 in which

the conductive substrate is a conductive metal substrate or a non-metallic

conductive substrate.

3. The electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer adsorbed on a conductive substrate of claim 2 in which

the metal substrate is chosen from the group consisting of copper, gold, silver,

palladium, platinum, and aluminum.

4. The electrochemical method for filling, repairing, or preventing voids and

the non-metallic conductive substrate is a doped semiconductor or a

conducting polymer.

5. The electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer adsorbed on a conductive substrate of claim 4 in which

the doped semiconductor is chosen from the group consisting of copper, gold, silver,

palladium, platinum, aluminum, n-type silicon, p-type silicon, polysilicon,

amorphous silicon, gallium arsenide, gallium arsenide phosphide, germanium.

6. The electrochemical method for filling, repairing, or preventing voids and

the conducting polymer is chosen from the group consisting poly(pyrrole),

poly (aniline), and poly(thiophene).

7. The electrochemical method for filling, repairing, or preventing voids and

the combination of the adsorbed layer and the substrate function as a molecular

electronic device chosen from the group consisting of optical, alternate logic, and

molecular memory devices.

8. The electrochemical method for filling, repairing, or preventing voids and

the soluble molecule is 1, 2-diaminobenzene.

9. The electrochemical method for filling, repairing, or preventing voids and

the process is terminated when the anodic current attributed to oxidation of

1, 2-diaminobenzene falls to 0.1% or less of its peak value.

10. The electrochemical method for filling, repairing, or preventing voids and

the molecular layer is chosen from the group consisting of self-assembled or

physisorbed organic monolayers, adsorbed polymer layers, crystalline or amorphous

films of monomeric organic molecules, and films composed of inorganic particles.

11. The method of claim 10 in which the self-assembled physisorbed organic

monolayers are about 0.5 to 4.0 nanometers in thickness, the adsorbed polymer

layers are between about 0.5 and 50.0 nanometers in thickness, the crystalline or

amorphous films of monomeric organic molecules are between about 0.3 and about

100.0 nanometers in thickness, and the films composed of inorganic particles are

between about 1.5 and about 100.0 nanometers in thickness.

12. The electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer adsorbed on a conductive substrate of claim 10 in which

the molecular layer is a self-assembled monolayer made from aliphatic and aromatic

monolayer-forming molecules that contain terminal thiol, disulfide, carboxylate,

isonitrile, amine, hydroxamate, phosphate, phosphonate, alkoxysilane, or halosilane

groups, or free radicals or aryl halides that can be covalently coupled to the surface

of the metal substrate.

13. The electrochemical method for filling, repairing, or preventing voids and

the organic films are made by adsorption of poly(pyrrole), poly(aniline, or

poly(thiophene).

14. The electrochemical method for filling, repairing, or preventing voids and

inorganic molecular film is a metal phosphonate, metal-cyanide network,

metallocene, metalloporphyrin, or metallopthalocyanine.

15. The electrochemical method for filling, repairing, or preventing voids and

the inorganic nanoparticle film is made of a metal nanoparticles, carbon

nanoparticles, particles of semiconducting oxides, particles of 13-15 semiconductors

including GaAs and InP.

16. The electrochemical method for filling, repairing, or preventing voids and

particles of semiconducting oxides are Ti0₂, ZnO or Sn0₂, and the particles of 13-15

semiconductors are GaAs or InP.

17. The electrochemical method for filling, repairing, or preventing voids and

the chalcogenides are one or more of CdSe, CdTe, M0S2, and WS2.

18. The electrochemical method for filling, repairing, or preventing voids and

the multilayers of molecules are made of aromatic molecules or macrocyclic

compounds.

19. The electrochemical method for filling, repairing, or preventing voids and

the polymer precursor is chosen from the group consisting of 1, 2-diaminobenzene,

aniline and aminonaphthalene derivatives, and preferentially aromatic amines in

which the aromatic ring contains at least one other electron-donating group.

20. The electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer adsorbed on a conductive substrate of claim 19 in which

the electron-donating group I chosen from the group consisting of amino, hydroxy,

or alkoxy, aromatic amines, aromatic alcohols, N-alkyl pyridium salts,

vinylbenzenes, and vinylpyridines.

21. An electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer between about 0.30 and about 100 nanometers in

thickness adsorbed on a conductive substrate comprising:

electrochemically introducing an amine functionality at defects in the

molecular or polymeric layer by immersing the coated substrate in a solution of an

aniline or diaminobenzene derivative and electropolymerizing;

adding a crosslinking agent containing two or more epoxy groups in

acetonitrile or dichloromethane to cross-link the polymer.

22. An electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer between about 0.30 and about 100 nanometers in

thickness adsorbed on a conductive substrate comprising:

depositing metal or metal oxides at the voids or defects to act as

underpotentially deposited hydrophilic attachment sites for insulating or less

conductive materials; and

growing or adhering an insulating material to the hydrophilic attachment

sites.

23. The electrochemical method for filling, repairing, or preventing voids

and defects in a molecular layer adsorbed on a conductive substrate of claim

22 in which the metal is copper or gold and the insulating material is

1, 10-decanediylbis(phosphonic acid).

24. A method of measuring film quality of in a molecular layer between about

0.30 and about 100 nanometers in thickness adsorbed on a metal or other

electronically conductive substrate; electrochemically oxidizing or reducing a

soluble molecule to a polymeric form by dissolving the soluble molecule in an

electrolyte solution, immersing the metal substrate in the solution, and applying an

appropriate potential to electropolymerize the molecule where the potential is at a

level less than that which would cause oxidative desorption or decomposition of the

molecular layer; and

imaging the deposits of polymer to assess the number of defects or voids.

25. An electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer between about 0.30 and about 100 nanometers in

thickness adsorbed on a conductive substrate comprising:

immersing the coated substrate in an aqueous electrolyte solution containing

insulated metal oxides derived from metal ions that are soluble at low pH and form

insoluble oxides or hydroxides at higher pH;

applying a current with a sufficiently negative potential to cause hydrogen to

be evolved from the contacting aqueous electrolyte solution thereby producing a

local increase in pH and hence the local precipitation of insulating polymers or metal

oxides at the voids and defects.

26. The method of claim 24 in which the metal ions are chosen from the group

consisting of Fe³⁺, Fe²⁺, Al³⁺, Zr⁴⁺, Co²⁺, Ni²⁺, and Zn²⁺.

27. An electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer between about 0.30 and about 100 nanometers in

thickness adsorbed on a conductive substrate comprising:

surface-catalyzing polymethylene in a diazomethane or diazomethane

derivative carrier to allow access of the diazomethane or the diazomethane

derivative carrier to the catalytic metal surface, thereby depositing polymethylene

only where defects or voids in the film are present.

28. The method of claim 27 in which an alkyl-containing derivative

of diazomethane is used.

29. The method of claim 27 in which a fluorinated containing derivative of

diazomethane is used.

30. An electrochemical method for filling, repairing, or preventing voids and

defects in a molecular layer between about 0.30 and about 100 nanometers in

thickness adsorbed on a conductive substrate comprising:

chemically adsorbing a soluble molecular inorganic compound to the voids

and defects;

reacting with a second compound to convert the adsorbed soluble molecular

inorganic compound to an insoluble inorganic material; and

repeating the adsorbing and reacting steps to grow the inorganic material in

layer-by-layer fashion to fill the voids and defects.

31. The method of claim 29 in which the second compound is water or

hydrogen sulfide.

32. The method of claim 29 in which the second compound is chosen from the

group consisting of oxides, sulfides, fluorides, nitride, and oxynitrides of transition

metals and post-transition elements, and oxides, sulfides, fluorides, nitrides, and

oxynitrides of the lanthanides.