Transparent conducting indium-tin-oxide(ITO) film as full front electrode in Ⅲ–Ⅴ compound solar cell

The application of transparent conducting indium-tin-oxide （ITO） film as full front electrode replacing the conven- tional bus-bar metal electrode in III-V compound GalnP solar cell was proposed. A high-quality, non-rectifying contact between ITO and 10 nm N＋-GaAs contact layer was formed, which is benefiting from a high carrier concentration of the terrilium-doped N＋-GaAs layer, up to 2×10^19 cm^-3. A good device performance of the GalnP solar cell with the ITO electrode was observed. This result indicates a great potential of transparent conducting films in the future fabrication of larger area flexible III-V solar cell.

Preparation of High Quality Indium Tin Oxide Film on a Microbial Cellulose Membrane Using Radio Frequency Magnetron Sputtering

Microbial cellulose （MC） membranes produced by Acetobacter xylinum NUST4.1,were used as flexible substrates for the fabrication of transparent indium tin oxide （ITO） electrodes.Transparent and conductive ITO thin films were deposited on MC membrane at room temperature using radio frequency （RF） magnetron sputtering.The optimum ITO deposition conditions were achieved by examining crystalline structure,surface morphology and op-toelectrical characteristics with X-ray diffraction （XRD）,scanning electron microscopy （SEM）,atomic force mi-croscopy （AFM）,and UV spectroscopy.The sheet resistance of the samples was measured with a four-point probe and the resistivity of the film was calculated.The results reveal that the preferred orientation of the deposited ITO crystals is strongly dependent upon with oxygen content （O2/Ar,volume ratio） in the sputtering chamber.And the ITO crystalline structure directly determines the conductivity of ITO-deposited films.High conductive [sheet resis-tance ～120 Ω·square-1 （Ω·sq-1）] and transparent （above 76%） ITO thin films （240 nm thick） were obtained with a moderate sputtering power （about 60 W） and with an oxygen flow rate of 0.25 ml·min-1 （sccm） during the deposi-tion.These results show that the ITO-MC electrodes can find their potential application in optoelectrical devices.

Electrical and optical properties of indium tin oxide/epoxy composite film

The electrical and optical properties of the indium tin oxide （ITO）/epoxy composite exhibit dramatic variations as functions of the ITO composition and ITO particle size. Sharp increases in the conductivity in the vicinity of a critical volume fraction have been found within the framework of percolation theory. A conductive and insulating transition model is extracted by the ITO particle network in the SEM image, and verified by the resistivity dependence on the temperature. The dependence of the optical transmittance on the particle size was studied. Further decreasing the ITO particle size could further improve the percolation threshold and light transparency of the composite film.

Temperature-dependent bias-stress-induced electrical instability of amorphous indium-gallium-zinc-oxide thin-film transistors

The time and temperature dependence of threshold voltage shift under positive-bias stress（PBS） and the following recovery process are investigated in amorphous indium-gallium-zinc-oxide（a-IGZO） thin-film transistors. It is found that the time dependence of threshold voltage shift can be well described by a stretched exponential equation in which the time constant τ is found to be temperature dependent. Based on Arrhenius plots, an average effective energy barrier Eτ stress= 0.72 eV for the PBS process and an average effective energy barrier Eτ recovery= 0.58 eV for the recovery process are extracted respectively. A charge trapping/detrapping model is used to explain the threshold voltage shift in both the PBS and the recovery process. The influence of gate bias stress on transistor performance is one of the most critical issues for practical device development.

Low Temperature DC Sputtering Deposition on Indium-Tin Oxide Film and Its Application to Inverted Top-emitting Organic Light-emitting Diodes

Indium tin oxide （ITO） ultrathin films were prepared on glass substrate by DC （direct current） magnetron sputtering technique with the assistance of H2O vapor to avoid potential surface damage. The film properties were characterized by X-ray diffraction （XRD） technique, four-point probe method and spectrophotometer. The results show that the deposited ITO film with introduced H2O during sputtering process was almost amorphous. The average visible light transmission of 100 nm ITO film was around 85% and square resistivity was below 80 Ω/square. The film was used as the transparent anode to fabricate an inverted top-emitting organic light-emitting diodes （IT-OLEDs） with the structure of glass substrate/Alq3 （40 nm）/NPB （15 nm）/CuPc （x nm）/ITO anode （100 nm）, where the film thickness of CuPc was optimized. It was found that the luminance of this IT-OLEDs was improved from 25 cd/m^2 to more than 527 cd/m^2 by increasing the thickness of CuPc, and luminance efficiency of 0.24 lm/W at 100 cd/m^2 was obtained, which indicated that the optimized thickness of CuPc layer was around 15 nm.

Double-layer indium doped zinc oxide for silicon thin-film solar cell prepared by ultrasonic spray pyrolysis

Indium doped zinc oxide （ZnO：In） thin films were prepared by ultrasonic spray pyrolysis on corning eagle 2000 glass substrate. 1 and 2 at.% indium doped single-layer ZnO：In thin films with different amounts of acetic acid added in the initial solution were fabricated. The 1 at.% indium doped single-layers have triangle grains. The 2 at.% indium doped single-layer with 0.18 acetic acid adding has the resistivity of 6.82 × 10^-3 Ω. cm and particle grains. The doublelayers structure is designed to fabricate the ZnO：In thin film with low resistivity （2.58 × 10^-3 Ω. cm） and good surface morphology. It is found that the surface morphology of the double-layer ZnO：In film strongly depends on the substratelayer, and the second-layer plays a large part in the resistivity of the doublewlayer ZnO：In thin film. Both total and direct transmittances of the double-layer ZnO：In film are above 80% in the visible light region. Single junction a-Si：H solar cell based on the double-layer ZnO：In as front electrode is also investigated.

Low-Frequency Noise in Amorphous Indium Zinc Oxide Thin Film Transistors with Aluminum Oxide Gate Insulator

Low-frequency noise（LFN） in all operation regions of amorphous indium zinc oxide（a-IZO） thin film transistors（TFTs） with an aluminum oxide gate insulator is investigated. Based on the LFN measured results, we extract the distribution of localized states in the band gap and the spatial distribution of border traps in the gate dielectric,and study the dependence of measured noise on the characteristic temperature of localized states for a-IZO TFTs with Al2 O3 gate dielectric. Further study on the LFN measured results shows that the gate voltage dependent noise data closely obey the mobility fluctuation model, and the average Hooge＇s parameter is about 1.18×10^-3.Considering the relationship between the free carrier number and the field effect mobility, we simulate the LFN using the △N-△μ model, and the total trap density near the IZO/oxide interface is about 1.23×10^18 cm^-3eV^-1.

Sulphurization of the Electrochemically Deposited Indium Sulphide Oxide Thin Film and Its Photovoltaic Applications

The post-deposition heat treatment (annealing) for the electrochemically deposited thin film is often necessary in order to improve its crystallinity. In the present study, the electrochemically deposited indium sulfide oxide thin film was annealed in sulphure atmosphere for 60 min at 150℃ and 300℃. The impact of the annealing process on the composition, crystal structure, and surface morphology of the thin film was investigated. In addition, superstrate heterojunction solar cells based on the annealed film as a buffer layer and tin sulphide as an active layer were fabricated and characterized. They showed diode-like behavior under dark condition and a relatively small photovoltaic effect under AM1.5 illumination condition.

Contact resistance asymmetry of amorphous indium–gallium–zinc–oxide thin-film transistors by scanning Kelvin probe microscopy

In this work, a method based on scanning Kelvin probe microscopy is proposed to separately extract source/drain（S/D） series resistance in operating amorphous indium–gallium–zinc–oxide（a-IGZO） thin-film transistors. The asymmetry behavior of S/D contact resistance is deduced and the underlying physics is discussed. The present results suggest that the asymmetry of S/D contact resistance is caused by the difference in bias conditions of the Schottky-like junction at the contact interface induced by the parasitic reaction between contact metal and a-IGZO. The overall contact resistance should be determined by both the bulk channel resistance of the contact region and the interface properties of the metalsemiconductor junction.

Lowering the Operational Voltage of Single-Layer Polymer Electroluminescent Devices by Using CuO_x Modifying Indium-Tin Oxide Electrode

In this study it is demonstrated that oxygen-plasma-generated CuOx can enhance the holes injection from ITO anode into polymer layer in single-layer polymer EL devices. The possible reason for this enhancement is because the ITO anode modified with CuOx possesses much higher work function than pure ITO anode, which reduces the barrier for hole-injection and further lowers the operational voltage of the polymer EL devices. The work function shift is probable due to the oxygen-plasma-generated CuOx can store more releasable oxygen, and the releasable oxygen in turn changes the oxygen concentration just near ITO surface, which will shift the work function of ITO anode.

Preparation of indium tin oxide targets with a high density and single phase structure by normal pressure sintering process

The present work mainly describes the technology for preparing indium-tin oxide （ITO） targets by cold isostatic pressing （CIP） and normal pressure sintering process. ITO powders were produced by chemical co-precipitation and shaped into an ITO green compact with a relative density of 60% by CIP under 300 MPa. Then, an ITO target with a relative density larger than 99.6% was obtained by sintering this green compact at 1550℃ for 8 h. The effects of forming pressure, sintering temperature and sintering time on the density of the target were inves- tigated. Also, a discussion was made on the sintering atmosphere.

High-throughput fabrication and semi-automated characterization of oxide thin film transistors

High throughput experimental methods are known to accelerate the rate of research,development,and deployment of electronic materials.For example,thin films with lateral gradients in composition,thickness,or other parameters have been used alongside spatially-resolved characterization to assess how various physical factors affect the material properties under varying measurement conditions.Similarly,multi-layer electronic devices that contain such graded thin films as one or more of their layers can also be characterized spatially in order to optimize the performance.In this work,we apply these high throughput experimental methods to thin film transistors(TFTs),demonstrating combinatorial channel layer growth,device fabrication,and semi-automated characterization using sputtered oxide TFTs as a case study.We show that both extrinsic and intrinsic types of device gradients can be generated in a TFT library,such as channel thickness and length,channel cation compositions,and oxygen atmosphere during deposition.We also present a semi-automated method to measure the 44 devices fabricated on a 50 mm×50 mm substrate that can help to identify properly functioning TFTs in the library and finish the measurement in a short time.Finally,we propose a fully automated characterization system for similar TFT libraries,which can be coupled with high throughput data analysis.These results demonstrate that high throughput methods can accelerate the investigation of TFTs and other electronic devices.

Positive gate bias stress-induced hump-effect in elevated-metal metal-oxide thin film transistors

Under the action of a positive gate bias stress, a hump in the subthreshold region of the transfer characteristic is observed for the amorphous indium-gallium-zinc oxide thin film transistor, which adopts an elevated-metal metal-oxide structure. As stress time goes by, both the on-state current and the hump shift towards the negative gate-voltage direction. The humps occur at almost the same current levels for devices with different channel widths, which is attributed to the parasitic transistors located at the channel width edges. Therefore, we propose that the positive charges trapped at the back-channel interface cause the negative shift, and the origin of the hump is considered as being due to more positive charges trapped at the edges along the channel width direction. On the other hand, the hump-effect becomes more significant in a short channel device （L=2 μm）. It is proposed that the diffusion of oxygen vacancies takes place from the high concentration source/drain region to the intrinsic channel region.

模压成型压力对氧化铟锡(ITO)靶材性能影响研究

以化学共沉淀-煅烧法制备的纳米ITO粉体为原料,通过模压、冷等静压成型,采用常压烧结法制备了ITO靶材,研究了模压成型压力对ITO靶材相对密度、电阻率和晶粒尺寸的影响。结果表明,模压成型压力60 MPa且烧结条件适宜时,制得的ITO靶材相对密度为99.81%、电阻率为1.707×10^(-4)Ω·cm、平均晶粒尺寸为7.62μm。研究结果可为ITO靶材的致密化与大型化生产提供借鉴。

射频磁控溅射工艺参数对掺钨氧化铟锡透明导电薄膜性能的影响

ITO薄膜是目前应用最为广泛的透明导电薄膜,通过在ITO中掺杂其他金属可以进一步改善ITO薄膜的光学和电学性能。本文采用射频(RF)磁控溅射法制备了掺钨氧化铟锡(ITO∶W)透明导电薄膜,研究了薄膜厚度、表面形貌、晶体结构以及光学和电学性能与各溅射参数之间的关系。当溅射功率大于40 W时,制备的ITO∶W薄膜为方铁锰矿结构的多晶薄膜,此时薄膜表面光滑平整而且具有良好的结晶性。在基板温度320℃、溅射功率80 W、溅射时间15 min、工作气压0.6 Pa条件下得到了光学和电学性能优良的ITO∶W薄膜,其方块电阻为10.5Ω/、电阻率为4.41×10^(-4)Ω·cm,对应的载流子浓度为2.23×10^(20)cm^(-3)、迁移率为27.3 cm^(2)·V^(-1)·s^(-1)、可见光(400~700 nm)范围内平均透射率为90.97%。此外,本研究还发现通过调节基板温度影响氧元素的状态可以改变ITO∶W薄膜的电学性能。

有源层溅射工艺及后退火温度对IZO TFT电性能的影响

为了提高氧化物薄膜晶体管的器件性能,以掺In氧化锌(IZO)为有源层,原子层沉积法(ALD)沉积的Al2O3薄膜为栅介层,制备了基于IZO的薄膜晶体管(IZO TFT),研究了IZO薄膜制备工艺中溅射气体氩氧流量比、溅射压强和后退火温度等工艺参数对TFT器件电学性能的影响。结果表明,在恰当的氩氧比和反应气压以及相对较高的退火温度下制备的IZO TFT具有良好的电学特性,当氩氧流量比为60:20 sccm、溅射压强为0.5 Pa、空气气氛中以250℃退火1 h时后,IZO TFT器件的整体电学特性表现较优,其迁移率高达31 cm^(2)/(V·s),开关电流比大于108。相对过低或过高的氩氧比会导致IZO有源层中氧空位含量过低或过高,从而降低TFT器件性能。过低的退火温度不足以使栅介质的Al-OH转变成Al-O以及空气中的氧扩散进入IZO体内钝化氧空位,因此器件性能较差。

IGZO薄膜晶体管生物传感器无标记检测强直性脊柱炎

为了快速检测强直性脊柱炎血清学分子标志物人体白细胞抗原(HLA-B27),开发了一种基于人体白细胞抗原B27(HLA-B27)功能化的氧化铟镓锌(IGZO)薄膜晶体管生物传感器。利用射频磁控溅射技术和微纳加工工艺制备了IGZO薄膜晶体管(IGZO TFT),采用3-氨丙基三乙氧基硅烷(APTES)和抗体对IGZO TFT进行修饰,制备出针对HLA-B27检测的生物传感器。实验结果表明,功能化的IGZO TFT生物传感器具有稳定的电学特性和传感性能。传感器对HLA-B27的检测极限为1 pg/mL,在1 pg/mL至100 ng/mL的范围内均有良好的线性响应。这说明所设计的高性能生物传感器能够有效检测出强直性脊柱炎的标志物。此外,IGZO TFT可以扩展为传感器阵列平台,实现对某种疾病多种标志物的联合检测,在便携式床旁诊断设备的应用中具有巨大潜力。

退火温度对ITO/Cu/AZO透明导电薄膜结构及性能的影响

采用射频与直流磁控交替溅射法在石英玻璃载玻片上制备了氧化铟锡(ITO)/Cu/Al掺杂ZnO(AZO)(45 nm/10 nm/45 nm)组合结构的透明导电薄膜,并在不同退火温度下对薄膜进行真空热处理。利用X射线衍射仪(XRD)、紫外-可见分光光度计、四探针电阻测试仪等表征手段,系统地研究了退火温度对ITO/Cu/AZO复合薄膜晶体结构和光电性能的影响。结果显示,经过不同温度的真空退火处理,薄膜的晶体结构和导电性能得到显著改善和提高,薄膜可见光平均透过率随着退火温度的升高先增加后降低。对比发现,在气压5×10^(-3)Pa、温度150℃下退火制备的ITO/Cu/AZO结构薄膜表现出最佳的综合性能,薄膜具有较强的(222)和(440)晶面衍射峰,在400~800 nm光波范围平均透过率约为80.5%,电导率约为1.76×10^(3) S/cm,综合品质因数达到约2.12×10^(-3)/Ω。

IAZO薄膜晶体管的制备与性能研究

为了探究退火温度对IAZO薄膜晶体管器件光电性能的影响,采用射频溅射单溅射法,并在(400~700)℃的范围内制备了一系列真空退火后的IAZO薄膜晶体管。分别对IAZO薄膜表面形貌、内部结构、元素组成和价态组成进行分析,采用半导体参数仪及搭配的探针台测试电学性能测试。采用紫外可见分光光度计测试薄膜透过率。结果表明,随着退火温度的升高,器件的电学性能先呈现上升趋势,达到峰值后开始下降。在500 ℃真空退火1 h后,IAZO TFT饱和迁移率为0.18 cm2/(V·s)、阈值电压为3.35 V、亚阈值摆幅为0.10 V/decade、开关比为1.13*108。IAZO薄膜透光率达到90 %以上、光学带隙达到4.1 eV,器件性能达到最佳。

低温快速制备基于溶液工艺的高性能氧化铟薄膜及晶体管

利用脉冲紫外线辅助热退火在200℃的低温条件下,5 min内制备了基于溶液工艺的氧化铟薄膜及薄膜晶体管.对比传统热退火,研究了脉冲紫外线辅助热退火对氧化铟薄膜的表面形态、化学结构和电学特性的影响.实验结果表明,脉冲紫外线辅助热退火方式能够在短时间内实现改善氧化铟薄膜的质量及薄膜晶体管的性能.原子力显微镜和场发射扫描电子显微镜结果显示该薄膜表面较传统热退火制备薄膜表面更为致密平坦.X射线光电能谱测试表明,脉冲紫外线辅助热退火处理后会产生氧空位,从而提高载流子浓度,改善了氧化铟薄膜的导电性.此外,对比研究了紫外线辅助热退火对氧化铟薄膜晶体管电气性能的影响.结果表明器件的电学特性得到了明显改善,亚阈值摆幅降低至0.12 mV/dec,阈值电压为7.4 V,电流开关比高达1.29×107,场效应迁移率提升至1.27 cm^(2)/(V·s).因此,脉冲紫外线辅助热退火是一种简单、快速的退火方式,即使在低温条件下也能快速提高氧化铟薄膜和薄膜晶体管的性能.