CN1321465C - Coulomb island style rectifying monomolecular diode and preparation thereof - Google Patents

Abstract

The present invention relates to a coulomb island type rectification unimolecular diode and a manufacture method thereof. The present invention is characterized in that a polymethyl methacrylate / poly (methyl methacrylate-methacrylamide) double-layer adhesive is coated on a silicon dioxide substrate; an etch groove is generated on the surface of the silicon dioxide substrate by electron beams, and metal is evaporated in the groove to form a metal nanometer wire. Both ends of the metal nanometer wire are added with voltage to be broken, and two metal nanometer electrodes are formed. The metal nanometer electrodes are soaked in ethanol solution of alkyl hydrosulfide, and mercaptan films are formed on the electrode surfaces. Toluene solution containing C59N, C81N or C59B is dropped on the nanometer electrodes. Transient direct-current bias voltage is applied to both ends of the electrodes, and the coulomb island type rectification unimolecular diode with the rectification effect is formed by the two electrodes and the organic molecule adsorbed on the electrode mercaptan film near the other electrode. The coulomb island type rectification unimolecular diode has the advantages of small size and low energy consumption, and has wide application prospect on single-electron circuits, molecular integrated circuits, selecting circuits and switching circuits.

Description

Coulomb island style rectification unimolecule diode and preparation method thereof

Technical field:

The invention belongs to unimolecule diode technologies field, particularly relate to Coulomb island style rectification unimolecule diode of nanoscale and preparation method thereof.

Background technology:

U.S.'s " physical comment bulletin " (Phys.Rev.Lett., 1993,70,218) introduced the rectification type molecule diode that constitutes by polar molecule, it is coupled together by molecular multilayer by two relative metal nano electrodes and constitutes, because an end of the polar molecule that is adopted obtains electronics easily, the other end loses electronics easily, so electric current can along a direction by and can not pass through in the other direction along it, make this molecule diode have the function of rectification.Because what connect between two electrodes is molecular multilayer,, make the operating current of diode be difficult to reduce the energy consumption height so rectifying effect is the common result of electric current by a plurality of molecules; And,, improve the integrated level of nano molecular device so be unfavorable for further reducing the size of diode owing to comprise multi-layer film structure in this molecule diode.

U.S.'s " American Chemical Society's newspaper " (J.Amer.Chem.Soc.1998,120,8486) introduced the resonance tunnel-through type diode that constitutes by individual molecule, what adopt is the organic molecule of symmetrical configuration and energy level symmetry, one section electrically conductive core is arranged in the middle of this molecule, across one section nonconducting strand, formed tunnel junction respectively and between two electrodes, electronics can only be tunneling on the electrically conductive core or from electrically conductive core from electrode and be tunneling on the electrode, and this electrically conductive core is a coulomb island.No matter this resonance tunnel-through type diode is from the space structure of diode or all be symmetrical in view of the level structure of organic molecule, this symmetry makes resonance tunnel-through type diode only have single resonance tunneling effect, and operating current is bigger, can not be used for single electron circuit and molecular rectifying circuit.

Summary of the invention:

The invention provides a kind of Coulomb island style, have unimolecule diode of rectification function and preparation method thereof.

Coulomb island style rectification unimolecule diode of the present invention, it is characterized in that: nonconducting mercaptan film that a bed thickness 0.5-1.7 nanometer is arranged respectively on two metal nano electrode surfaces, organic molecule is adsorbed on the mercaptan film of one of them metal nano electrode, and that absorbing molecules and two electrodes nearest apart from another electrode have just constituted the Coulomb island style unimolecule diode with rectifying effect; Described organic molecule is that a class has the molecule that single electron occupies track (Single electron molecularorbital, abbreviation SOMO), comprises C ₅₉N, C ₈₁N or C ₅₉B molecule, its single electron occupy track up and down energy level have asymmetric characteristics: promptly the highest on the molecular entergy level occupies attitude (HOMO) and minimum not occupy attitude (LUMO) unequal with respect to the energy level spacing that single electron occupies track.

The preparation method of Coulomb island style rectification unimolecule diode of the present invention, comprise and on silicon dioxide substrates, be coated with earlier polymethyl methacrylate/poly-(methyl methacrylate monomethyl third rare acid amides) double-deck glue, generate the etching groove with electron beam on this surface, to this surface evaporation metal, in groove, form the nano wire of this metal again; Break to form the nano-electrode of two metals then to metal nanometer line at this metal nanometer line two ends making alive; It is characterized in that preparation process after this is:

(1) cleans the metal nano electrode of above-mentioned preparation with organic solvent, then this metal nano electrode is placed in the oxygen flame and removes impurity, put into the ethanolic solution of the alkyl hydrosulfide of 0.01-5.00 millimolar concentration, soaked 24-48 hour, the metal nano electrode surface forms self-assembled monolayer; From solution, take out this metal nano electrode that there is monofilm on the surface, and clean with organic solvent;

(2) toluene solution of the organic molecule of preparation 0.1-1.0 millimolar concentration; Selected organic molecule is that a class has the molecule that single electron occupies track, comprises C ₅₉N, C ₈₁N or C ₅₉The B molecule;

(3) toluene solution of the organic molecule that step (2) is prepared drops in through step (1) surface treated and has on the metal nano electrode of monofilm, applies an of short duration Dc bias at these nano-electrode two ends then; Wash nano-electrode with organic solvent; The organic solvent that remains on the electrode is vapored away;

Described organic solvent comprises acetone, absolute ethyl alcohol or toluene.

Among the present invention, because organic molecule polarizes under effect of electric field, organic molecule after the polarization all moves towards the big electrode of electric-force gradient, just be adsorbed on the mercaptan film surface after touching the mercaptan film, other organic molecules that do not adsorb are on the position of departing from center between two electrodes the organic molecule of resulting Coulomb island style rectification unimolecule diode then by the organic solvent flush away; Owing to the tunnelling current between the tunnelling electrode is decayed rapidly along with the increase of distance is index, therefore the electric current between two electrodes mainly flow through the distance surface absorption go up that nearest absorbing molecules of electrode of organic molecule, and other absorbing molecules not have to contribute to tunnelling current substantially.Therefore diode utilization of the present invention is the characteristic of the conduction of individual molecule, reflection also be the electronic transport character of individual molecule, this makes the size of whole diode to reduce greatly.

Because the organic molecule among the present invention has single electron and occupies track, and this track energy level up and down has asymmetric characteristics, so electronics is tunneling on the organic molecule or the process that is tunneling on the metal nano electrode from organic molecule is a single electron transport process from metal nano electrode, by adjusting voltage, can control diode and once only allow an electronics pass, make the operating current of diode reach theoretical minimum value.

Because preparation method of the present invention forms the nonconducting self-assembled monolayer mercaptan of one deck film on the metal nano electrode surface organic molecule and metal nano electrode are separated, therefore, can be self-assembled into monofilm by the mercaptan of choosing different chain length, for example can select butane group mercaptan, decyl mercaptan or Stearyl mercaptan for use, thickness with control mercaptan film, distance D can be at 1.7nm to 0.5nm between organic molecule and the nearest electrode thereby make, and its reverse breakdown voltage then can be-0.7 volt to-1.9 volts; So can pass through to change the thickness adjusted distance D of molecular film, thereby make this unimolecule diode have the reverse breakdown voltage of appointment; When the reverse voltage at unimolecule diode two ends was no more than reverse breakdown voltage, the unimolecule diode did not have reverse current to pass through, and forward can have electric current to flow through, thereby unimolecule diode of the present invention has the function of rectification.

Coulomb island style unimolecule diode of the present invention, because the organic molecule that adopts has single electron and occupies track, its current delivery process is the transport process of single electron, so, electric current is very little during conducting state, and energy consumption is very low, and oppositely cut-off region is in the coulomb blockade district, reverse current is zero in theory, thereby has the characteristic of good rectification; Because the single electron transmission course is a tunnelling process, compole was short when electronics was worn then, so the current response speed of Coulomb island style unimolecule diode of the present invention is fast, switching speed is fast.Because whole unimolecule diode is a double tunnel junction system, by changing the resistance or the electric capacity of tunnel junction, can adjust the reverse breakdown voltage of diode, the controlled diode of this performance is at the single electron circuit, and there is very application prospects molecular switch circuit aspect.

Description of drawings:

Fig. 1 is the structural representation of unimolecule diode of the present invention;

Fig. 2 is the volt-ampere characteristic that the unimolecule diode to embodiment records;

Fig. 3 is when the unimolecule diode is carried out forward voltage, the variation schematic diagram of Molecular Electronic Structure;

Fig. 4 is when the unimolecule diode is carried out reverse voltage, the variation schematic diagram of Molecular Electronic Structure.

Embodiment:

Embodiment 1:

1, be ready to the pair of metal nano-electrode earlier, the method that for example can adopt Britain's " nature " (nature, 1997,389,699) or U.S.'s " Applied Physics wall bulletin " (Appl.Phys.Lett., 1999,75,301) to provide prepares electrode:

(1) on silicon dioxide substrates 1, is coated with polymethyl methacrylate/poly-double-deck glue of (the rare acid amides of methyl methacrylate-methyl-prop) (PMMA/P (MMA-MAA)) as electron sensitive resist; Go out the groove that width and the degree of depth are about 200 nanometers with the electron beam lithographic method in this bilayer glue surface etch, the accelerating voltage of the electron beam that is adopted is 20 kilovolts, and bundle spot size is 0.1 micron; Utilize the thermal evaporation instrument to steam the gold or the copper of about 15 nanometer thickness on this surface again, deposition forms metal nanometer line in groove thus; During evaporated metal, vacuum degree must be higher than 1.0 * 10 ^-3Handkerchief, control silicon dioxide substrates temperature is a room temperature, the thickness of metal film in the evaporation can be controlled by monitor; With the ion beam etching machine polymethyl methacrylate/poly-(the rare acid amides of methyl methacrylate-methyl-prop) double-deck glue is removed then, promptly obtain metal nanometer line;

(2) add a voltage at the metal nanometer line two ends, regulate this voltage, when this voltage reaches 470 millivolts, metallic atom moves under electric field action, make the metal nano thread breakage, form the metal nano electrode 4 that wide about 30 nanometers, thick about 5 nanometers, about 5 nanometers in gap, crack, end radius of curvature are about 5 nanometers in fracture place;

2, clean the metal nano electrode of above-mentioned preparation with acetone, then this metal nano electrode is placed in the oxygen flame and removes impurity, the ethanolic solution of putting into the decane mercaptan of 1 millimolar concentration soaks 36 hours, and (or the ethanolic solution of putting into the decane mercaptan of 5 millimolar concentrations soaked 24 hours, or the ethanolic solution of putting into the decane mercaptan of 0.01 millimolar concentration soaked 48 hours), promptly form self-assembled monolayer 2 on metal nano electrode 4 surfaces; This nano-electrode is taken out from solution, clean, remove remaining decane thiol molecule with absolute ethyl alcohol;

3, with purity be the C of 99.0-99.9% ₅₉N is dissolved in the analytically pure toluene solution, is mixed with the C of 0.1-1.0 millimolar concentration ₅₉The toluene solution of N;

4, with the C of the 0.1-1.0 millimolar concentration of above-mentioned preparation ₅₉The toluene solution of N drops in the surface to be had on two metal nano electrodes of self-assembled monolayer, apply 5 volts of of short duration Dc biases again (this direct voltage can change in 0.1-100 lies prostrate scope at these nano-electrode two ends, the general 1-5 volt that adopts), be about to power supply and nano-electrode two end in contact and once just disconnect, be equivalent to 10 this time of contact that applies approximately ^-3-10 ^-1Second; Since effect of electric field, C ₅₉The N molecule is polarized, and the molecule after the polarization moves towards the big electrode of electric-force gradient, at decane thiol molecule film and C ₅₉Under the interaction of N molecule, C on the metal nano electrode A surface adsorption ₅₉The N molecule; Wash this nano-electrode with absolute ethyl alcohol, the C that is not adsorbed ₅₉The N molecule is by the absolute ethyl alcohol flush away; Apart from the nearest C of electrode B ₅₉ N absorbing molecules 3 and two electrode A, B have just constituted the Coulomb island style unimolecule diode with rectifying effect.

The decane mercaptan that step 2 is used replaces with Stearyl mercaptan or butane group mercaptan respectively, repeats the preparation process of above-mentioned 1-4, can prepare the Coulomb island style unimolecule diode with rectifying effect equally.

5, contrast this three kinds of unimolecule diodes, electrode surface is covered with Stearyl mercaptan film, decane mercaptan film and butane group mercaptan film respectively, make that distance D is respectively 1.7,1.1,0.5 nanometer between organic molecule and the nearest electrode, record their volt-ampere curve respectively, shown in a, the b of Fig. 2, c curve.Table 1 has been listed the cut-in voltage U of the molecule diode of these 3 kinds of different D values _Th, puncture voltage U _(BR), reverse dc l _{R (sat)}

The electrical parameter of the unimolecule diode of the different D values of table 1:3 kind

	D(nm)	U th(V)	U (BR)(V)	I R(sat)(nA)
					a	1.7	0.45	-0.7	0
b	1.1	0.45	-1.0	0
					c	0.5	0.45	-1.9	0

7, above-mentioned three Coulomb island style unimolecule diodes are connected in the circuit with 0.6 volt of AC power and 100 megohm resistance string respectively, observe the change in voltage at resistance two ends with oscilloscope, find that ohmically voltage only has that part of greater than 4.5 millivolts of forward, and reverse voltage is zero always, and the Coulomb island style unimolecule diode of susceptible of proof the present invention preparation has rectified action thus.

The operation principle of Coulomb island style rectification unimolecule diode of the present invention is: the SOMO track 8 of organic molecule and the energy between the HOMO track 7 differ Δ Eg ₁, the energy difference between LUMO track 9 and the SOMO track 8 is Δ E _G2, HOMO and LUMO orbital energy are asymmetric with respect to the SOMO orbital energy, i.e. Δ E _G1≠ Δ E _G2, and Δ E _G1With Δ E _G2Have than big-difference; The big more rectifying effect of difference is remarkable more.Because the input electronics has directly influenced the single electron tunnelling current of molecule in bibarrier tunnel junction with take the energy that electronics needs away from molecule different on the molecule, its volt-ampere characteristic shows rectifying effect.If C ₁, R ₁Be electric capacity and the resistance between A electrode and the organic molecule 3, C ₂, R ₂Be electric capacity and the resistance between B electrode and the organic molecule 3, and C ₁＞C ₂(if C ₁＜C ₂, to the operation principle did not influence); Fig. 3 and Fig. 4 have provided when the unimolecule diode is carried out forward and reverse voltage respectively, the variation schematic diagram of Molecular Electronic Structure.The concrete course of work is as follows:

(1), because C ₁＞C ₂, and the energy of Fermi level 5 and SOMO track 8 equates, when at C ₂On dividing potential drop V ₂Greater than C ₁On dividing potential drop V ₁The time, electronics is easier to be tunneling on the organic molecule 3 from metal electrode B, works as V ₂During less than Ec, Ec is a coulomb charging energy, the coulomb blockade when external electric field is not enough to overcome the single electron tunnelling, and this moment, forward current was zero, diode presents bigger resistance, is in the dead band; When forward voltage continue to increase, make V ₂Greater than Ec, at this moment an electronics is tunneling to this molecule from the B electrode, occupied on the SOMO track 8 as shown in Figure 3 that less than the room, thereby caused Fermi level 5 Ec that moves up, form new Fermi level 6, and original SOMO track has just become new HOMO track 10 because of having occupied two electronics, and the energy of new HOMO track 10 raises than original Fermi level 5 When $\frac{\mathrm{\&Delta;}\mathrm{<figure-callout\; id="2"\; label="E\; g"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_2}{2}<\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec},$ Electronics on the new HOMO track 10 can be tunneling on the A electrode from this molecule, produces tunnel current, at this moment forward conduction voltage $U_{\mathrm{th}}=\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec};$ And work as $\frac{\mathrm{\&Delta;}\mathrm{<figure-callout\; id="2"\; label="E\; g"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_2}{2}>\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec},$ Need increase voltage this moment again, and electronics could be from HOMO track 10 tunnelling metal electrode A, forward conduction voltage $U_{\mathrm{th}}=\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">C</figure-callout>}}_2}\&times;(\frac{\mathrm{\&Delta;}\mathrm{<figure-callout\; id="2"\; label="E\; g"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_2}{2}-\mathrm{Ec}),$ Along with voltage is higher than U _Th, diode presents low resistive, the pipe conducting;

(2), when applying a reversed electric field, because V at the diode two ends ₂Greater than V ₁, the easier elder generation of electronics is tunneling on the metal electrode B from organic molecule 3, works as V ₂During＜Ec, the electronics on this molecule SOMO track 8 can not be tunneling on the metal electrode B, and this moment, reverse current was zero, and diode presents bigger resistance, is in the dead band; When reverse voltage continue to increase, make C ₂On dividing potential drop V ₂Greater than coulomb charging energy Ec, at this moment an electronics is tunneling to the B electrode from this molecule, SOMO track 8 has lost an electronics, become new LUMO track 11, thereby caused Fermi level 5 to move down Ec, form new Fermi level 6, the energy of new LUMO track 11 raises than original Fermi level 5

When $\frac{\mathrm{\&Delta;<figure-callout\; id="1"\; label="E\; g"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_1}{2}<\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec}$ The time, electronics can be tunneling on the new LUMO track 11 of molecule from the A electrode, produces tunnel current, at this moment reverse breakdown voltage $U_{\left(\mathrm{BR}\right)}=\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec},$ When $\frac{\mathrm{\&Delta;<figure-callout\; id="1"\; label="E\; g"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_1}{2}>\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec}$ The time, must further increase voltage, just can make on electronics is tunneling to new LUMO track 11 on the molecule from the A electrode, produce tunnel current; The reverse breakdown voltage of this moment

$U_{\left(\mathrm{BR}\right)}\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">C</figure-callout>}}_2}\&times;(\frac{\mathrm{\&Delta;<figure-callout\; id="1"\; label="E\; g"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_1}{2}-\mathrm{Ec});$

(3), can obtain the forward conduction voltage U from top analysis _ThWith reverse breakdown voltage U _(BR)Be subjected to the capacitor C between molecule and the electrode ₁, C ₂And the Δ Eg of molecule ₁, Δ Eg ₂Influence.Table 2 has been listed different Δ Eg ₁, Δ Eg ₂Influence to the rectifying effect of diode:

The different Δ Eg of table 2 ₁, Δ Eg ₂U under the condition _(BR), U _ThExpression formula

Can clearly find out from table 2, when $\frac{\mathrm{\&Delta;<figure-callout\; id="1"\; label="E\; g"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_1}{2}<\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec},$ $\frac{\mathrm{\&Delta;<figure-callout\; id="2"\; label="E\; g"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_2}{2}<\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec}$ The time, the unimolecule diode does not have rectifying effect, therefore according to monomolecular Δ Eg ₁, Δ Eg ₂Span, the unimolecule diode can be divided into three kinds:

1), when $\frac{\mathrm{\&Delta;<figure-callout\; id="1"\; label="E\; g"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_1}{2}>\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec},$ $\frac{\mathrm{\&Delta;<figure-callout\; id="2"\; label="E\; g"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_2}{2}<\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec}$ The time, $\frac{U_{\mathrm{th}}}{U_{\left(\mathrm{BR}\right)}}=\frac{C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\frac{2\mathrm{Ec}}{\mathrm{\&Delta;E}{g}_1-2\mathrm{Ec}}<1,$ The fixing Δ Eg of organic molecule ₁, work as C ₁And C ₂When differing big more, the ratio of conducting voltage and puncture voltage is more little; Fixation of C ₁, C ₂Constant, change monomolecular Δ Eg ₁, Δ Eg ₁Big more, the ratio of conducting voltage and puncture voltage is also more little, and the rectifying effect of unimolecule diode is obvious more.

2), when $\frac{\mathrm{\&Delta;<figure-callout\; id="1"\; label="E\; g"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_1}{2}<\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec},$ $\frac{\mathrm{\&Delta;<figure-callout\; id="2"\; label="E\; g"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_2}{2}>\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec}$ The time, $\frac{U_{\mathrm{th}}}{U_{\left(\mathrm{BR}\right)}}=\frac{C_1}{{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">C</figure-callout>}}_2}\&times;\frac{\mathrm{\&Delta;E}{g}_2-2\mathrm{<figure-callout\; id="2"\; label="Ec"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">Ec</figure-callout>}}{2\mathrm{Ec}}>1,$ Fixing monomolecular Δ Eg ₂, work as C ₁And C ₂Size when differing big more, the ratio of conducting voltage and puncture voltage is big more; Fixation of C ₁, C ₂Constant, change monomolecular Δ Eg ₂, Δ Eg ₂Big more, the ratio of conducting voltage and puncture voltage is also big more, and the rectifying effect of unimolecule diode is obvious more.

3), when $\frac{\mathrm{\&Delta;<figure-callout\; id="1"\; label="E\; g"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_1}{2}>\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec},$ $\frac{\mathrm{\&Delta;<figure-callout\; id="2"\; label="E\; g"\; filenames="C0213845600101.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_2}{2}>\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec}$ The time, $\frac{U_{\mathrm{th}}}{U_{\left(\mathrm{BR}\right)}}=\frac{\mathrm{\&Delta;E}{g}_2-2\mathrm{Ec}}{\mathrm{\&Delta;E}{g}_1-2\mathrm{Ec}},$ The ratio of the conducting voltage of unimolecule diode and puncture voltage is fully by Δ Eg at this moment ₁, Δ Eg ₂Size decision, and C ₁, C ₂Irrelevant, as Δ Eg ₁With Δ Eg ₂Differ big more, then the rectifying effect of unimolecule diode is obvious more.

In the present embodiment, the C of unimolecule diode ₁Be C approximately ₂Twice, C ₅₉Approximate satisfied (the Δ Eg of N molecule ₂)/2＜Ec＜(Δ Eg ₁)/2, at this moment, because C ₁Equal 2 times of C ₂, therefore $U_{\mathrm{th}}=\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;\mathrm{Ec},$ Be approximately equal to Ec, this is a constant substantially numerical value, and $U_{\left(\mathrm{BR}\right)}=\frac{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}\&times;(\frac{\mathrm{\&Delta;<figure-callout\; id="1"\; label="E\; g"\; filenames="C0213845600101.png,C0213845600111.png"\; state="\{\{state\}\}">E</figure-callout>}{g}_{}{}_1}{2}-\mathrm{Ec}),$ Because C ₂＜C ₁So, C ₂Change some U _(BR)Have change clearly,, change C by using the thiol molecule of different chain length ₅₉The distance D of N and arest neighbors electrode, thus C changed ₁And C ₂Ratio, can know from Fig. 2 and see the cut-in voltage U of three unimolecule diodes _ThSubstantially keep 0.45 volt constant, and reverse breakdown voltage U _(BR)Change to-1.9 volts from-0.7 volt.So, can change puncture voltage U by changing the electric capacity of bibarrier tunnel junction _(BR)Scope, reach the purpose of the reverse breakdown voltage of artificial control unimolecule diode.

Claims (2)

1, a kind of Coulomb island style rectification unimolecule diode, it is characterized in that: nonconducting mercaptan film that a bed thickness 0.5-1.7 nanometer is arranged respectively on two metal nano electrode surfaces, organic molecule is adsorbed on the mercaptan film of one of them metal nano electrode, and that absorbing molecules and two electrodes nearest apart from another electrode have just constituted the Coulomb island style unimolecule diode with rectifying effect; Described organic molecule comprises C ₅₉N, C ₈₁N or C ₅₉The B molecule.

2, a kind of preparation method of Coulomb island style rectification unimolecule diode, comprise and on silicon dioxide substrates, be coated with earlier polymethyl methacrylate/poly-(the rare acid amides of methyl methacrylate-methyl-prop) double-deck glue, generate the etching groove with electron beam on this surface, to this surface evaporation metal, in groove, form the nano wire of this metal again; Break to form the nano-electrode of two metals then to metal nanometer line at this metal nanometer line two ends making alive; It is characterized in that preparation process after this is:

(1) cleans the metal nano electrode of above-mentioned preparation with organic solvent, this metal nano electrode is placed in the oxygen flame removes impurity then; Put into the ethanolic solution of the alkyl hydrosulfide of 0.01-5.00 millimolar concentration, soaked 24-48 hour, the metal nano electrode surface forms self-assembled monolayer; From solution, take out this metal nano electrode that there is monofilm on the surface, and clean with organic solvent;

(2) toluene solution of the organic molecule of preparation 0.1-1.0 millimolar concentration; Selected organic molecule is that a class has the molecule that single electron occupies track, comprises C ₅₉N, C ₈₁N or C ₅₉The B molecule;

(3) toluene solution of the organic molecule that step (2) is prepared drops in through step (1) surface treated and has on the metal nano electrode of monofilm, and applying a time at these nano-electrode two ends then is 10 ^-3-10 ^-1The Dc bias of second; Wash nano-electrode with organic solvent; The organic solvent that remains on the electrode is vapored away;

Described organic solvent comprises acetone, absolute ethyl alcohol or toluene.

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