| The wide band gap semiconductor materials have been developed rapidly,and the preparation methods and properties semiconductor materials have become important directions in the field of semiconductor devices.Tungsten trioxide(WO3)and diamond are both important wide bandgap semiconductor materials with many excellent physical and chemical properties,such as optics,electricity and heat.WO3 has many outstandingt optical and electrical properties such as electrochromic,photochromic,photocatalytic and gas sensing,which has been widely used in ion batteries,smart windows,gas sensors,UV photodetectors,resistive switches and so on.The nano-structure WO3 has a large surface area,a significant surface effect and a strong absorption ability to electromagnetic waves.Therefore,it is ideal solar energy absorbing and photocatalytic material.At the same time,diamond(bandwidth 5.47 e V)shows many excellent properties including high radiation resistance,low thermal expansion coefficient,wide potential window,high hole mobility,good chemical stability,high p-type doped hole mobility and strong corrosion resistance.So it has great potential applications in biosensors,high-temperature,high-frequency and high-power devices,electrochemical electrodes and other fields,which has beenregarded as an important research direction for the preparation and applications of high-performance semiconductor devices.In a word,it is of great significance to study the electrical properties of these two kinds of materials and explore the new properties of the composite structures.In this paper,the preparation and properties of tungsten oxide,diamond and two composite structures were studied.The obtained achievements are as follows:1.The pure WO3 film and Ti O2 doped WO3 films have been fabricated by pulsed laser deposition and the effects of Ti O2 on the electrochromic properties of WO3 have been investigated.In the sulfuric acid-glycerol solution,the colored films with different Ti O2 doping concentration exhibited different blue.The pure WO3 and2% doped Ti O2-WO3 films showed dark blue,while the 5% and 10% doped Ti O2-WO3 films showed sapphire blue.The doping of Ti O2 extends the visible light absorption region of the WO3 films.In the process of coloring,the crystal structures of the four samples turned to the blue tungsten bronze structure(Hx WO3)from the WO3 of the three oblique phase.In the colored state,the H+ in the lattice reduced the valence state of some tungsten(W)ions,so that the W element in the film has three mixed valence states such as +6,+5 and +4.The coloring effect of the films results in an increase of the W5+ and W4+ concentration in the film and a decrease of the W6+concentration.There was a linear relationship between the increase of the W5+concentration and the injection coefficient x(Hx WO3,x<0.25).When H+ was injected into the thin film,there were a large number of W5+(17.04%)2.Fabricate the boron-doped diamond(BDD)films and modify gold nanoparticles(Au NPs)on the surface of diamond for dopamine biosensor electrodes.Compared with the traditional sputtering annealing method,twice sputtering annealing method can effectively improve the Au nanoparticle density and specific surface area,reduce the particle size.And then improve the reactivity of the Au NPs/BDD electrode to dopamine,and enhance the current response intensity.The dopamine detection limit can reach 3×10-6 mol/L.After analysis,the diamond itself has excellent electrochemical stability,high sensitivity to detection of metal ions or organic compounds in water and non-aqueous media.The Au nanoparticles have agood enrichment and specificity effect on dopamine.The interaction of the two factors greatly improves the sensitivity and selectivity of dopamine determination.3.By the sol-gel method and hydrothermal method,we prepared the non intentionally doped n-WO3 nanorods(WO3 NRs)on the boron-doped diamond.The n-WO3 NRs/p-diamond heterojunction was obtained,and the structure was characterized and analyzed.The I-V test shows that the turn-on voltage of the heterojunction is 3.3 V at room temperature and the ideality factor is about 23.8.When the voltage is ± 5 V,the n-WO3 NRs/p-diamond heterojunction rectifier is up to295.The band structure analysis,the established ?EC(2.83 e V)of heterojunction is much higher than the ?EV(0.06 e V).Therefore,the hole conduction rectifying characteristic mainly depends on the injected hole in the valence band of the diamond.4.In this paper,the semiconductor characteristics and current transport mechanism of n-WO3 NRs/p-diamond heterojunction devices were discussed at room temperature to high temperature(290 o C).The p-n heterojunction devices showed good thermal stability and good rectifying properties from room temperature to 290 oC.As the temperature increased,the turn-on voltage decreased from 3.3 V(room temperature)to 0.1 V(290 o C).The ideal factor of the heterojunction device decreased gradually as the temperature increased.At high temperatures(over 270 o C),the value of n approaches the value of the ideal p-n heterojunction 2.0.The characteristic trap energy(Et)of the heterojunction is 50 me V.According to the ln(Is)vs 1/T curve,the activation energy of heterojunction(Ea)is calculated to be 0.70 e V.In the low voltage region,the I-V characteristic follows the exponential relationship.The exponent is close to 1,which indicates that the ohmic contacts of the heterojunctions are good at various temperatures.In the mediate voltage region,the I-V of the heterojunction follows the law of I~exp(?V)law due to the wide bandgap p-n diode complying with the compound tunneling conduction mechanism.The value of ? is close to the value of the ideal vacuum diode,indicating that the heterojunction has good thermal stability.In the high voltage region,the I-V characteristic curves follow the power exponent relation caused by the space charge limited current(SCLC)in the wide band gap semiconductor material.At higher temperatures,more and morethermally activated carrier fill traps,the power exponent decreases close to 2,as shown by the SCLC conductivity without trap confinement.In this paper,the methods of preparing Ti O2 doped tungsten oxide films and Au-diamond electrodes were introduced,and their structure and electrical properties were analyzed.In this paper,the n-WO3/p-diamond heterojunction was prepared by sol-gel method and hydrothermal method for the first time.The experimental results show that the tungsten oxide/diamond heterojunction devices exhibited excellent electrical properties at room temperature and good stability at high temperatures.Dopamine is an important neurotransmitter in the brain,and the Au NPs/BDD electrode has a good current response to dopamine,which is of great significance in medical detection. |
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