Optical And Electric Characteristic Of Semiconductor Functional Films Of Vanadium Oxide And Its Application

With the researcher’s explorement, photoelectric device is becoming moreminiaturization, power comsumption, miniaturization, and intelligentize,high-performance of photoelectric device and its integrated technology have becomeresearch hotspot. Vanadium oxide has been paid more attenttion because of its uniquephotoelectric characteristcs in the application of uncooled infrared detector,photoelectric regulator, smart window, optical storage and sensors, etc. Thephotoelectric device application of vanadium oxide has a high requirement inuniformity, but the multi-value of valence and quality deviation has a large influenceon the uniformity. Therefore, fabrication process of vanadium oxide plays a key rolein photoelectric device to obtain a controllable film surfurce and elements. In thispaper, different substrates were been employed for vanadium oxide deposition.Through ajusting the parameter of process, the qaulity of vanadium oxide film can beoptimized and the corresponding photoelectric characteristics has been studied.The rapid thermal process (RTP) and reactive sputtering methods were used inour research for preparation of vanadium oxide. The microstructure andphotoelectricity properties of vanadium oxide were characterized by advancedmeasuring tools as Scanning Electron Microscope (SEM), Atomic Force Microscopy(AFM), X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS),8-FTerahertz Time Domain Spectroscopy (THz-TDS) and Semiconductor ParameterAnalyzer (SPA). The mechanisms of vanadium oxide phase transition under differentincentives were studied by atom diffusion, surface interface electronic structure,electron transport mechanism and CAFM.Firstly, the vanadium oxides were prepared on the Polyimide (PI) and c-Al2O3substrates. The impacts on the temperature and time during the thermal oxidationprocess were elucidated. Vanadium oxide thin films with good phase transitionproperties were successfully prepared. The optimized results as follows:(1)60nm metal vanadium on the PI substrate after the thermal oxidation (380℃/120s) formed vanadium oxide thin films which was formed had good transformation performances, the V4+content of the membrane is51.05%,phase transition temperature is41℃, thermal hysteresis loop width is5℃.(2)100nm metal vanadium on the c-Al2O3substrate after the thermal oxidation(500℃/60s) formed vanadium oxide thin films which was formed had goodtransformation performances, the V4+content of the membrane is78.59%,phase transition temperature is49℃, thermal hysteresis loop width is4℃.(3) The surface microstructure changes of the vanadium oxide under differenttemperatures were tested by in-situ heating test system of AFM. As thetemperature increases, the surface morphology of the vanadium oxide filmchanged from strip into the rounded particles. The phase transition ofvanadium oxide films is caused by structural changes.Secondly, the THz wave modulation characteristics of the vanadium oxide thinfilms were tested by THz-TDS. Research results showed that with the increase ofexcitation light power, the modulation rates of the vanadium oxide thin films wereincreased. The modulation rate of vanadium oxide on PI substrate was73.8%under100mW optical excitation power, and the modulation rate of vanadium oxide onc-Al2O3substrate was70.7%under800mW optical excitation power. The repeatedtesting results shown that vanadium oxide thin films after the optimized processconditions of preparation have reversible and stable THz wave modulationcharacteristics. Through the surface temperatures changes of the vanadium oxideunder optical excitation and combined with electron transport mechanism, we candraw a conclusion that the optical excitation vanadium oxide thin films produce phasetransition was caused by carrier’s internal migration.Finally, we investigated the resistive switching (RS) behaviors of Cu/VOx/Cucell by applying voltages. The results of I-V curves showed that the cell had morestable switching behaviors when the vanadium oxide thin films close to the vanadiumpentoxide stoichiometry. The RS behaviors showed that the polarization ofCu/VOx/Pt、 Cu/VOx/Al、 Cu/VOx/Cu were unipolar, bipolar, and non-polar,respectively. Based on the RS and CAFM results, we can draw a conclusion that themechanisms of Cu/VOx/Pt and Cu/VOx/Cu belong to ionic conduction mechanism,the former was oxygen vacancy conductive filaments, the other was conductivefilaments, and the conductive mechanism of VOx/Cu/Al was effect of space chargelimited current (SCLC). In a word, the conditions of preparation of vanadium oxide thin films and theoptical and electric properties were studied in detail, and the phase transformationmechanisms were explored under different excitation methods. The results wereexpected to provide the scientific basis for the subsequent research and the design ofvanadium oxide-based photoelectric devices.