Prepartion And Investigation Of Metal/Gallium Nitride Composite Material

Gallium nitride(GaN),a semiconductor with a wide direct band gap,has the band gap width of up to 3.4 eV.Particularly,due to its excellent optical properties,GaN has great potential for application in blue LED and other light-emitting devices.In addition,the crystal structure characteristics of GaN provide the stable and secure operation for many strong electrical mechanisms in various sensors,high power and high frequency microwave devices under the high temperature,high frequency and high pressure.Therefore,the preparation and utilization of multi-functional GaN materials are conducive to improving their practical application value.In this dissertation,based on the growth of 5?m thick GaN epitaxial wafer by hydride vapor phase epitaxy(HVPE)as the research object,the preparation of metal-GaN composites and their applications in electrochemical sensing and raman spectroscopy were discussed.The main contents are as follows:1.Porous GaN nanostructures were fabricated by photoelectrochemical wet etching method with the non-aqueous solution ionic liquids as etchant.Influence of the etching voltage and etching time on the surface morphology of porous GaN nanostructures was studied,and the mechanism was also investigated.The optimal experimental conditions are7 V and 15 min.Subsequently,in a conventional three-electrode system,porous GaN was used as the working electrode.The effective loading of noble metal nanoparticles on porous GaN were prepared by the electrochemical means.Take the case of precious metal Pt,the experimental results show that cyclic voltammetry is an effective way to fabricate metal nanoparticles.2.A simple two-step electrodeposition process was developed to decorate the porous GaN electrode with Pd and Pt(Pd-Pt)nanocomposites in order to fabricate a novel nitrite sensor.The concrete experimental process is as follows:In the first step,Pt was electrodeposited on porous GaN by cyclic voltammetry(CV).In the second step,Pd was electrodeposited on the as-prepared Pt-modified porous GaN(Pt/PGaN)by chronoamperometry(CA).In the end,the Pd-Pt/porous GaN sensor was successfully assembled for electrochemical detection of nitrite.A series of experimental test results indicate the obtained Pd-Pt/PGaN sensor provided a wide linear range,lower detection limit,high selectivity and excellent stability for nitrite.Moreover,the sensor exhibited a good recovery for nitrite determination in practical sample analysis.3.Using porous GaN prepared by wet etching as the support material,silver nanoparticles(AgNPs)were successfully electrodeposited on porous GaN by cyclic voltammetry to fabricate the surface enhanced raman scattering(SERS)substrates.The influence of different electrochemical deposition cycles on the particle size of Ag nanoparticles was investigated.The experimental results indicated that enhancement of SERS which was prepared by the deposition cycle number of 100 was best.With the study and analysis of the calibrated Rhodamine 6,the detection limit of the obtained Ag/porous GaN is 10~-1414 mol,the enhancement factor is up to 10~8.Moreover,the Ag/porous GaN substrates have good repeatability and long-term stability.