The Effect of Oxygen Partial Pressure during Active Layer Deposition on Bias Stability of a-InGaZnO TFTs

The effect of oxygen partial pressure （Po2） during the channel layer deposition on bias stability of amorphous indium-gallium-zinc oxide （a-IGZO） thin film transistors （TFTs） is investigated. As Po2 increases from 10% to 30%, it is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on the x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies （Or） within the a-IGZO layer is suppressed by increasing Po2. Meanwhile, the low-frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops with increasing Po2. Therefore, the improved interface quality with increasing Po2 during the channel layer deposition can be attributed to the reduction of interface Ov-related defects, which agrees with the enhanced bias stress stability of the a-IGZO TFTs.

A novel closed-loop vacuum silicon microgyroscope

A novel closed-loop control strategy of a silicon microgyroscope （SMG） is proposed. The SMG is sealed in metal can package in drive and sense modes and works under the air pressure of 10 Pa. Its quality factor reaches greater than l0 000. Self-oscillating and closed-loop methods based on electrostatic force feedback are adopted in both measure and control circuits. Both single side driving and sensing methods are used to simplify the drive circuit. These dual channel decomposition and reconstruction closed loops are applied in sense modes. The testing results demonstrate that useful signals and guadrature signals do not interact with each other because of the decoupling of their phases. Under the condition of a scale factor of 9. 6 mV/（（°） .s）, in a full measurement range of±300 （°）/s, the zero bias stability reaches 28 （°）/h with a nonlinear coefficient of 400 × 10^-6 and a simulated bandwidth of more than 100 Hz. The overall performance is improved by two orders of magnitude in comparison to that at atmospheric pressure.

Quadrature error and offset error suppression circuitry for silicon micro-gyroscope

The reasons for inducing quadrature error and offset error are analyzed and the expressions of quadrature error and offset error are induced. The open-loop system analysis indicates that, in order to avoid the appearance of harmonic peaks, the frequency difference δf between drive mode and sense mode must be less than 1/（2Qy）. In order to eliminate the effects of the quadrature error and the offset error, as well as the inherent non- linearity in the capacitance-type sensors, a closed-loop feedback control circuit with quadrature correction is designed. The experimental results indicate that the quadrature error and offset error are corrected. By comparing with open-loop detection, the closed-loop feedback control circuit with quadrature correction decreases the non-linearity of the scale factor from 16. 02% to 0. 35 %, widens the maximum rate capability from ± 270 （°）/s to ± 370 （°）/s and increases the stability of zero bias from 155. 2 （°）/h to 60. 6 （°）/h.

Illumination interface stability of aging-diffusion-modulated high performance InZnO/DyO_(x) transistors and exploration in digital circuits

In current study,the rare-reported solution-driven DyO_(x)films have been prepared to act as the dielectric layer of high performance InZnO/DyO_(x)thin film transistors(TFTs).Annealing temperature dependent thermal decomposition,morphology,crystallization behavior,and chemical compositions of DyO_(x) and InZnO films have been investigated respectively.Results have demonstrated that air-annealed InZnO/DyO_(x)TFTs possess the improved electrical performance,including ultrahigh on/off current ratio of 1×10^(9),larger saturation mobility of 12.6 cm^(2) V-1 s^(-1) and negligible hysteresis after 10 d aging diffusion in the relative humidity(RH)of 40%air ambient,which has been explored by the variable range-hopping(VRH)percolation model and energy band theory.The distinct illumination bias stability can be attributed to the generated various interface defects and concluded that the white light illuminated TFT behaves the higher stability with the smaller threshold voltage shift of 0.25 V.To confirm its feasible application in digital circuit,a resistor-loaded inverter based on InZnO/DyO_(x)TFTs has been constructed.A high gain of 10.1 and good dynamic response behavior have been detected at a low operating voltage of 2 V.As a result,it can be inferred that diffusion-induced enhanced carrier transporting mechanism is an economical and effective method to optimize the electrical performance of solution-derived InZnO/DyO_(x)TFTs,indicating its potential application prospects in flexible transparent electronics with low power consumption.

Influence of substrate temperature on the performance of zinc oxide thin film transistor

Top-contact thin film transistors（TFTs） using radio frequency（RP） magnetron sputtering zinc oxide （ZnO） and silicon dioxide（SiO;） films as the active channel layer and gate insulator layer,respectively,were fabricated.The performances of ZnO TFTs with different ZnO film deposition temperatures（room temperature, 100℃and 200℃） were investigated.Compared with the transistor with room-temperature deposited ZnO films, the mobility of the device fabricated at 200℃is improved by 94%and the threshold voltage shift is reduced from 18 to 3 V（after 1 h positive gate voltage stress）.Experimental results indicate that substrate temperature plays an important role in enhancing the field effect mobility,sharping the subthreshold swing and improving the bias stability of the devices.Atomic force microscopy was used to investigate the ZnO film properties.The reasons for the device performance improvement are discussed.

Diffusion-activated high performance ZnSnO/Yb_(2)O_(3) thin film transistors and application in low-voltage-operated logic circuits

The flourishing metal-oxide high-k dielectric materials have been regarded as the vital components of low voltage operated flexible transparent electronic devices.We herein report that ytterbium oxide(Yb_(2)O_(3))and ZnSnO(ZTO)thin films were firstly integrated into ZTO-based thin film transistors(TFTs)with superior performance.Results have indicated that the 500℃-annealed ZTO/Yb_(2)O_(3) TFTs possess the large saturation mobility of 9.1 cm^(2) V-1S^(-1) and the high on/off current ratio of 2.15×10^(7),which even surpass those of reported In-based TFTs.The deteriorative electrical properties in the aging process can be attributed to the carrier capture mechanism.However,the 460℃-processed TFTs demonstrate a tenfold increase in saturated mobility and an increase in on/off current ratio after 10 days aging.The inspiring electrical properties are attributed to the diffusion-activated carrier enhancement mechanism and electrons donor role of water molecular,which introduces a facile method to boost the device performance at lower processing temperatures.The neglected threshold voltage variations of 0.06 V and-0.2V have been detected after bias stability experiments.The superior bias stability can be attributed to the charge delay effect induced by the continuous electric field.Meanwhile,the ultrahigh on/off current ratio of 1.1×10^(7) and the recoverable transferring performance have verified the aging-activated mechanism.To confirm its potential application in digital circuits,a resistor-loaded inverter with gain of 5.6 has been constructed and good dynamic response behavior have been detected at a low voltage of 2V.As a result,it can be concluded that the high temperature annealing TFTs need immediate encapsulation,while the performance of the lower temperature processing samples can be optimized after aging treatment,indicating the potential prospect in low power consumption large-scale flexible transparent devices.