CN1424246A

CN1424246A - Organic metal complex nano wires and preparation thereof

Info

Publication number: CN1424246A
Application number: CN02151236.1A
Authority: CN
Inventors: 陈国荣; 莫晓亮
Original assignee: Fudan University
Current assignee: Fudan University
Priority date: 2002-12-12
Filing date: 2002-12-12
Publication date: 2003-06-18
Anticipated expiration: 2022-12-12
Also published as: CN1202001C

Abstract

A nano wire of organic metal match Ag(TCNQ) is prepared through plating a non-class Ag film on substrate by vacuum evaporating or sputter, loading it along with organic material TCNQ into a container, vacuumizing, sealing, heating to smelt said nano film to become liquid drops, and reacting to generate the nano wires basically perpendicular to the substrate. Its advantages are high electric bistable nature and good field emission characteristics.

Description

A kind of metal organic complex nano wire and preparation method thereof

Technical field

The invention belongs to field of nanometer technology, be specifically related to a kind of metal organic complex nano wire and preparation method thereof.

Background technology

Since Ijima S finds CNT, various nano wires such as MgO, metal and multiple simple substance, compound semiconductor or the like are subjected to increasing attention in every field, and they have wide application space at aspects such as nanoelectronic, light, magnetic devices.(document [1] Ijima S.[J] .Nature, 1991,354:56; [2] P.D.Yang, C.M.Lieber, [J] .Science, 1996,273:1836; [3] G.Fasl, K.Runge, [J] .Appl.Phys.Lett., 1997,70 (18): 2467; [4] K.Hiruma, M.Yazawa, T.Katsuyama, et al.[J] .Appl.Phys.Lett., 1995,77:447; [5] H.Z.Zhang, P.D.Yu, Y.Ding, et al.[J] .Appl.Phys.Lett., 1998,72:3458; [6] S.Forster, M.Antonietti, [J] .Adv.Mater., 1998,10:195; ).The charge transfer type metal organic complex is a kind of organic functional material of extensively being paid close attention to, and itself just has optics, the electrical properties of many uniquenesses.Have photochromic characteristic a bit with its film of making, can be used for optical storage; Apply certain electric field at a specific direction of its crystal and can present negative resistance charactertistic, and the resistivity of high and low two kinds of resistance states differs 10 ⁵～10 ⁷The order of magnitude promptly has tangible switching effect.([Z] W.Z.Wang, Y.Geng, Y.T. Qian, M.G.Ji, X.M.Liu, [J] .Adv..Mater., 1998,10:1479; [8] Z YHua, G R Chen, D Y Chen et al, [J] .IEEE Transactions on Consumer Electronics.1999,45 (1): 97) still do not see that so far the report that is made into nano wire (rod) is arranged.

Summary of the invention

The objective of the invention is to propose a kind of new nano wire, i.e. metal organic complex, and proposition corresponding preparation method.

From the component analysis of Ag (TCNQ) itself,, make it may become the nanometer " lead " of the lateral isolation of a kind of " natural " because of it has quasi-one-dimensional conductive characteristic.Among the present invention, be made into nano wire (rod), and further studied its physical property (particularly electricity with optics), and having scientific meaning aspect optical physics, the photochemical basic research, have wide practical use at aspects such as preparation field-effect transistor, an emission, Chu Qing.

The preparation metal organic complex nano wire Ag (TCNQ) that the present invention proposes, adopted vacuum saturated vapor reaction method, detailed process following (as shown in Figure 1):

1. with vacuum evaporation or other method, go up the Ag film of preparation one deck 5-20 nanometer thickness at substrate (silicon chip, glass etc.);

2. the rapid sample of making that the Ag film is arranged of previous step and organic material TCNQ are placed simultaneously a container (as glass tube etc.);

3. said vesse is vacuumized, be evacuated to 2 * 10 ^-3Pa is above with seal of vessel, separates with vacuum system;

4. place baking oven to heat above-mentioned vacuum tank, keep required temperature certain hour, the metal A g film on the substrate will react with the saturated vapor of TCNQ like this, finally generates Ag (TCNQ) organic coordination compound nano wire on substrate; Here holding temperature can be 55 ℃～150 ℃, and preferred temperature is 70 ℃～90 ℃.Holding time can be 15～40 minutes, and the preferred time is 20～30 minutes.The stoichiometric proportion of Ag and TCNQ 1: 1.

The nanowire growth temperature of Ag (TCNQ) material relatively low (≤150 ℃) has overcome some present nanotubes, the too high shortcoming of line preparation temperature, thereby easy and other process compatible.

Ag (TCNQ) nano wire of the present invention's preparation forms " forest " shape along arranging perpendicular to the direction of base plan basically with the whisker form, and this point is different with the film of chemistry and vacuum vapor deposition method preparation.The cross section of Ag (TCNQ) nano wire whisker is approximate to be square, and the length of side is less than 100 nanometers, and length (highly) is micron dimension.Fig. 2 be the silverskin of 20 nanometer thickness on the silicon substrate under 80 ℃ of conditions, the photo of the Ag that is prepared into (TCNQ) nano wire under electron microscope.Under the thin situation of silverskin, the Ag of generation (TCNQ) nano wire whisker length obviously reduces, and diameter variation is less relatively.

The present invention has also studied the electrical properties and the growth mechanism of the nano wire of Ag (TCNQ).

The unique character of Ag (TCNQ) is exactly its electrical bistable property and accurate one-dimensional electric.Ag among Fig. 2 (TCNQ) nano wire is constituted structure as shown in Figure 3 under the STM needle point, apply the scan bias voltage (at this moment needle point and sample room relative position remain unchanged) of triangular waveform at needle point and sample room.Shown in Figure 4 is the I-V curve of Ag (TCNQ) nano wire under the STM needle point.Curve 1 is corresponding to the triangle scan bias voltage ascent stage among the figure, and curve 2 is corresponding to descending branch.Can see that when the voltage on the sample during less than 1.7V, sample is in high-impedance state, tunnel current increases slowly with voltage; When the voltage of sample rose to about 1.7V (threshold voltage), the resistance of sample sharply reduced and enters low resistance state, and tunnel current sharply increases.At the 2nd section curve that bias voltage descends, Ag (TCNQ) still remains in low resistance state.But when bias voltage drop to-during the 0.2V left and right sides, resistance changes suddenly again, high-impedance state is got back in transition again.From the I-V curve as can be seen, under the high electric field action of STM needle point, the resistance of Ag (TCNQ) nano wire can have high resistant and low-resistance two states (electrical bistable property), and the transformation between two kinds of Resistance states of height can repeat.

In order to observe the electrical properties of Ag (TCNQ) nano wire vividerly, we use the AFM of conductive pinpoint to test the pattern and the map of current picture (shown in Figure 5) of a certain Ag (TCNQ) nano wire.Wherein left figure is the pattern picture, and right figure is the electric current picture.The needle point bias voltage is 1.8V, has surpassed the electric field threshold value (edge's field intensity is bigger) that changes in the field intensity of the edge of nano wire, and phase transformation has taken place, and be transformed into low resistance state (bright), and mid portion still is in high-impedance state (secretly).

Ag (TCNQ) nano wire also has a characteristic of emission is arranged.Fig. 6 is an I-V curve of emission.

In order to study the growth mechanism of Ag (TCNQ) nano wire, we will prepare the substrate of a bed thickness silverskin (about 100 nanometers) and the filamentary silver of a 0.2mm diameter, and they are tried to prepare Ag (TCNQ) with aforementioned with quadrat method.The result does not have any sign of Ag (TCNQ) of formation.This phenomenon explanation, the saturated vapor reaction method is not a gas-solid reaction process under the vacuum condition, but a gas-liquid reaction process.In the said temperature scope, solid-state silver and the saturated vapor of TCNQ can not react.But under the nanoscale situation, silver point drops to tens degrees centigrade of magnitudes, under the vacuum condition, the glass tube of sealing remains in the temperature environment more than 55 ℃, and the silverskin on this moment substrate in fact melts, form the nanometer droplet, at this moment the saturated vapor of TCNQ and silver hair are given birth to reaction, generate minimum solid-state Ag (TCNQ) crystal, vertically stand on the substrate, its top remains the little silver that is liquid condition and drips, and forms the system (as shown in Figure 6) of a solid-liquid-gas three-phase coexistence.Because Ag (TCNQ) is the predominant direction of crystal growth along the substrate vertical direction, along with reaction continues, the Ag of generation (TCNQ) more and more microscler one-tenth Ag (TCNQ) nano wire.Because the silver of liquid state is not that well-proportioned one deck is dispersed on the substrate during beginning, but exist with droplet state one by one, just being doomed Ag (TCNQ) film of last formation is not complete a sheet of Ag (TCNQ) monocrystalline, but arranges " forest " that form (Fig. 2) by the whisker of Ag (TCNQ) one by one.And,, because of all exhausting to grow, Ag stops at last so Ag (TCNQ) nano wire (brilliant Shall) top that generates is less owing to Ag in the growth course is consumed gradually.

Ag of the present invention (TCNQ) nano wire growth course is to carry out under the state of a balance, and the stoichiometric proportion of silver and TCNQ is 1: 1 in the Ag of Xing Chenging (TCNQ) the nano wire whisker at last.Growth temperature is very low, and condition is relatively easily controlled, easy and other process compatible in application facet.Because the good molectronics character that has of Ag (TCNQ) is considered to a kind of material of up-and-coming preparation molecular electronic device, thereby is made into nano wire and has scientific meaning and using value.

Description of drawings

Fig. 1 is the sample preparation schematic diagram of saturated vapor reaction method under the vacuum condition.

Fig. 2 is the electron scanning micrograph of Ag (TCNQ) film of the present invention's preparation.Wherein Fig. 2 (a) is for receiving line whisker cross-sectional view, and Fig. 2 (b) vertically arranges for the nano wire whisker.

Fig. 3 is for utilizing STM specimen schematic diagram.

Fig. 4 is the I-V curve of Ag (TCNQ) nano wire.

Fig. 5 is the afm image of Ag (TCNQ) nano wire.Wherein left side figure is the pattern picture, and right figure is the electric current picture.

Fig. 6 is the field emission I-V curve of Ag (TCNQ) nano wire.

Fig. 7 is Ag (TCNQ) nano wire growth mechanism schematic diagram.

Number in the figure: 1 is TCNQ powder art; 2 is the Ag film; 3 is substrate; 4 is the STM needle point; 5 is Ag (TCNQ) nano wire; 6 is the Ag drop.

The specific embodiment

For example, further describe the present invention below by experiment.

Be equipped with Ag (TCNQ) organic coordination compound nano wire with saturated vapor legal system under the vacuum condition, detailed process is:

On glass substrate, evaporate the Ag film of about 20 nanometer thickness of one deck with vacuum method; Then this film sample and organic material TCNQ are placed in the glass tube simultaneously, glass tube is vacuumized, to 2 * 10 ^-3Pa seals glass tube; Glass tube is placed baking oven, be heated to about 80 ℃, kept 20～30 minutes, Ag and TCNQ stoichiometric proportion are 1: 1, promptly obtain Ag (TCNQ) organic coordination compound nano wire.The photo of this nano wire under electron microscope as shown in Figure 2, its electrical bistable property as shown in Figure 4, pattern and map of current picture as shown in Figure 5, as seen this Ag (TCNQ) nano wire has good molectronics character.

Claims

1, a kind of metal organic complex nano wire is characterized in that being prepared by Ag (TCNQ), and its whisker form forms " forest " shape along arranging perpendicular to the direction of base plan basically, and the cross section of whisker is approximate to be square.

2, a kind of preparation method by the described metal organic complex nano wire of claim 1 is characterized in that adopting vacuum saturated vapor reaction method, and concrete steps are as follows:

(1) use vacuum method on substrate, to prepare the metal A g film of one deck 5-20 nanometer thickness;

(2) metal A g film sample and organic material TCNQ are placed a container simultaneously;

(3) said vesse is vacuumized, to 2 * 10 ^-3More than the Pa, with seal of vessel;

(4) container that vacuumizes is put into baking oven, required temperature certain hour is kept in heating, and the metal A g film on the substrate will react with the saturated vapor of organic material TCNQ, finally generates metal organic complex Ag (TCNQ) nano wire on substrate; Here holding temperature can be 55 ℃～150 ℃, and holding time can be 15～40 minutes, and metal organic complex Ag and TCNQ meet stoichiometric proportion.

3, preparation method according to claim 2 is characterized in that holding temperature is 70 ℃～90 ℃.

4, according to right 2 described preparation methods, it is characterized in that holding time is 20～30 minutes.