SOLUTION PROCESS FOR INSB NANOPARTICLES AND APPLICATION FOR IR DETECTORS

Abstract

This invention relates to a process for synthesizing InSb nanoparticles, a method to stabilize them, and a method to provide a photodetector to detect infrared light.

Claims

1. Process for the production of indium antimonide nanoparticles characterized in that a source of indium, a source of antimony and a reducing agent chosen from borohydrides and aluminium hydrides are combined in a solvent.

2. Process for the production of indium antimonide nanoparticles according to claim 1, characterized in that the solvent contains less than 10% by weight amines.

3. Process for the production of indium antimonide nanoparticles according to claim 1, characterized in that the reducing agent is selected from tetrahydroborates or trialkylhydroborates.

4. Process for the production of indium antimonide nanoparticles according to claim 1, characterized in that the nanoparticles are single-phase nanocrystals.

5. Process for the production of indium antimonide nanoparticles according to claim 1, characterized in that the source of antimony is an antimony(III) salt.

6. Process for the production of indium antimonide nanoparticles according to claim 1, characterized in that the source of indium and the source of antimony are combined firstly in a solvent, and the reducing agent is added to the resulting mixture.

7. Process for the production of indium antimonide nanoparticles according to claim 1, characterized in that the solvent comprises 10% by weight or more of an amine and the reducing agent is a trialkylborohydride.

8. Process for the production of indium antimonide nanoparticles according to claim 1, characterized in that the source of indium and the source of antimony are combined and heated to 100 C. or more.

9. Process for the production of indium antimonide nanoparticles according to claim 1, characterized in that the particles are stabilized by tetrafluoroborate, hexafluorophosphate or hexachloroantimonate anions by contacting the nanoparticle surface with aforementioned ligands.

10. A semiconducting electronic device comprising a layer of indium antimonide nanoparticles.

11. A semiconducting electronic device according to claim 10, characterized in that the device is a detector for infrared radiation

12. A method of providing a semiconducting device according to claim 10, comprising the steps: a) depositing a layer of indium nanoparticles on a substrate, b) providing electrodes to the layer, c) optionally heating the layer of nanoparticles.

13. Indium antimonide nanoparticle stabilized by tetrafluoroborate, hexafluorophosphate or hexachloroantimonate anions.

14. Process for the production of an indium antimonide nanoparticle stabilized by tetrafluoroborate, hexafluorophosphate or hexachloroantimonate anions according to claim 13, characterized in that such InSb nanoparticle is treated with tetrafluoroborate, hexafluorophosphate or hexachloroantimonate anions respectively.

15. Ink comprising InSb nanoparticles according to claim 12 dispersed in a liquid phase comprising one or more solvents.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 shows the X-ray diffraction spectrum using a Cu K x-ray source of InSb nanoparticles produced according to Example 1.

[0027] FIG. 2 shows the photoresponse of the InSb photodetector of Example 6 under broadband AM1.5 light (100 mW/cm.sup.2).

[0028] FIG. 3 shows the photoresponse of the InSb photodetector of Example 6 under monochromated light of 900 nm wavelength.

[0029] The examples below shall illustrate the invention without limiting it. The skilled person will be able to recognize practical details of the invention not explicitly mentioned in the description, to generalize those details by general knowledge of the art and to apply them as solution to any special problem or task in connection with the technical matter of this invention.

EXAMPLES

[0030] Materials:

[0031] Antimony (III) chloride (SbCl.sub.3, >99.99%), indium (III) chloride (InCl.sub.3, 99.999%), polyvinylpyrrolidone (PVP, average mol wt 10,000), triethylene glycol (TEG, >99.0%), lithium triethylborohydride (1 M in THF), sodium borohydride (NaBH.sub.4, 99%), and triethyloxonium tetrafluoroborate (Et.sub.3OBF.sub.4, >97.0%) were purchased from Sigma-Aldrich. Antimony (III) acetate (Sb(CH.sub.3COO).sub.3, 97%) was purchased from Alfa Aesar. Acetonitrile (99.8%) and isopropyl alcohol (IPA, 99.8%) were purchased from EMD Chemicals. Oleylamine (80-90%) was purchased from Acros Organics. Ethylene glycol (EG, 99.0%) was purchased from VWR. Millipore ultra-pure water was used, with resistivity >18.0 M-cm. All chemicals were used as-received.

[0032] Procedure: Antimony and indium salts and LiAlHEt.sub.3 were handled in a glovebox with <5 ppm oxygen and moisture levels. All other chemicals were added in air. All reactions were carried out using standard air-free techniques under a Schlenk line with constant stirring.

Example 1. Nanoparticle Synthesis Using LiAlHEt.SUB.3 .Reducing Agent

[0033] 22.1 mg InCl.sub.3, 28.9 mg Sb(CH.sub.3COO).sub.3, and 20 ml oleylamine were heated in a round bottom flask under vacuum to 110 C. and degassed at this temperature for 15 min. At this point, the reactant mixture was cloudy and light yellow. The reactants were then heated to 265 C. under nitrogen. Next 1.2 ml of lithium triethylborohydride solution was injected drop-wise in the flask. Upon addition of lithium triethylborohydride, the mixture immediately turned opaque brownish black. After allowing the reaction to proceed at 265 C. for 16 hours, single phase InSb nanoparticles could be obtained. Next the heat was removed and the nanoparticle solution was allowed to cool to room temperature.

[0034] The resulting particles are examined by X-ray diffraction (FIG. 1). The measured spectrum is in accordance with the reference peaks.

Example 2. Nanoparticle Synthesis Using NaBH.SUB.4 .Reducing Agent

[0035] 33.2 mg InCl.sub.3, 34.2 mg SbCl.sub.3, 0.1 g PVP, and 20 ml ethylene glycol were heated to 110 C. and held at this temperature for 15 min in a round bottom flask. The reaction mixture was initially placed under vacuum but was switched to nitrogen upon vigorous boiling around 100 C. At this point, the mixture was a colorless solution. The reactants were then heated to 150 C. under nitrogen, by which point the solution was yellowish and clear. 1 ml ultra-pure water was added to 0.0681 g NaBH.sub.4 in a separate vial, which dissolved within a minute and resulted in slight evolution of bubbles. The NaBH.sub.4 solution was then immediately injected drop-wise into the reaction mixture resulting in a dark black solution instantly. After allowing the reaction to proceed at 150 C. for 16 hours, single phase InSb nanoparticles could be obtained. Next the heat was removed and the nanoparticle solution was allowed to cool to room temperature.

Example 3. Nanoparticle Synthesis Using NaBH.SUB.4 .Reducing Agent

[0036] 221 mg InCl.sub.3, 228 mg SbCl.sub.3, 0.1 g PVP, and 50 ml triethylene glycol were heated under vacuum to 110 C. and degassed at this temperature for 15 min. At this point during the reaction, the mixture was a clear yellow-orange solution. Next, the reaction mixture was heated to 165 C. under nitrogen, resulting in a dark orange clear solution. In a separate vial, 20 ml triethylene glycol was added to 0.455 g NaBH.sub.4 and the mixture was sonicated followed by stirring for 30 min. After sonicating/stirring, the cloudy translucent white NaBH.sub.4 suspension was injected drop-wise to the reaction mixture, which turned opaque black instantly. The temperature of the reaction mixture was then raised to 200 C. After 16 hours of reaction time, single phase InSb nanoparticles could be obtained. Next, the heat was removed and the nanoparticle solution was allowed to cool to room temperature.

Example 4. Ligand Exchange Protocol and Ink Preparation

[0037] 4.5 g Et.sub.3OBF.sub.4 was dissolved in 50 ml of isopropanol and 50 ml of acetonitrile to prepare a ligand stock solution with total concentration of Et.sub.3OBF.sub.4 of 0.25 M. The reaction mixture (from examples 1, 2 or 3) was collected and centrifuged as-is at 10,000 rpm for 5 min. The supernatant was poured off and the solids were redispersed in 10 ml of Et.sub.3OBF.sub.4 stock solution using sonication. Next the resulting nanoparticle dispersion was centrifuged again at 8000 rpm for 5 min. The supernatant was poured off and the solids were redispersed in 10 ml of acetonitrile. The resulting ink was stable and free of agglomerates and was used to deposit films of InSb nanoparticles.

Example 5. InSb Film Preparation/Characterization

[0038] The ink prepared in example 4 was drop casted on a glass substrate to make a 0.1-10 m thick InSb layer. Next the film was heated at 400 C. for 10 s in a nitrogen environment to improve the electronic properties of the film.

Example 6

Photodetector Device Construction/Testing:

[0039] Two parallel metal electrodes were deposited on the InSb film by coating a commercial silver ink or sputtering a patterned gold layer. The electrodes were spaced 2 mm apart and were 10 mm in length. FIG. 2 shows a current vs. voltage plot of the InSb phtotodetector in dark vs light (AM 1.5, broadband light). Clearly the current value under light exposure is higher than under dark showing an appreciable photoresponse. FIG. 3 shows that the device is photoresponsive upon exposure to a monochromated infrared light source (in this case 900 nm).

[0040] Further combinations of the embodiments of the invention and variants of the invention are disclosed by the following claims.