The effect of annealing on the semiconductor in a thin film transistor

This study is concerned with an investigation of the effect of temperature annealing on the CdSe semiconductor in a thin film transistor. Electron microscopy shows that the CdSe film is polycrystalline. Annealing results in the growth of the crystallites until, for working thin film transistors, the crystallite size distribution becomes a log-normal one, with a mean crystallite size approximately equal to the thickness of the film. Annealing reduces the energy stored in the CdSe by converting grain boundaries from high to low angle ones and by reducing the grain boundary area.     

The effect of thermal annealing sequence on amorphous InGaZnO thin film transistor with a plasma-treated source–drain structure

In this paper, the effects of thermal annealing and the plasma treatment sequence on the performance of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) without conventional source/drain (S/D) layer deposition were investigated. We fabricated TFTs using two different processes, one where S/Ds were plasma-treated after thermal annealing, the second where the S/Ds were plasma-treated before annealing. The performance of the former exhibited a linear mobility of 4.97 cm²/V s, an on/off ratio of 4.6 × 10⁶, a V_th of 2.56 V, and a subthreshold slope of 0.65 V/decade. However, the TFT parameters of the latter sample were reduced to a linear mobility of 0.07 cm²/V s, an on/off ratio of 1.5 × 10⁵, a V_th of 2.33 V, and a subthreshold slope of 3.54 V/decade. It was shown that the sheet resistance of plasma-treated S/D areas increased after thermal annealing by about three orders of magnitude. As a result, the increase of the sheet resistance caused a decrease of TFT performance.     

The effect of annealing ambient on the characteristics of an indium-gallium-zinc oxide thin film transistor

In this study, the effects of different annealing conditions (air, O2, N2, vacuum) on the chemical and electrical characteristics of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFT) were investigated. The contact resistance and interface properties between the IGZO film and the gate dielectric improved after an annealing treatment. However, the chemical bonds in the IGZO bulk changed under various annealing atmospheres, which, in turn, altered the characteristics of the TFTs. The TFTs annealed in vacuum and N2 ambients exhibited undesired switching properties due to the high carrier concentration (>10(17) cm(-3)) of the IGZO active layer. In contrast, the IGZO TFTs annealed in air and oxygen ambients displayed clear transfer characteristics due to an adequately adjusted carrier concentration in the operating range of the TFT. Such an optimal carrier concentration arose through the stabilization of unstable chemical bonds in the IGZO film. With regard to device performance, the TFTs annealed in O2 and air exhibited saturation mobility values of 8.29 and 7.54 cm2/Vs, on-off ratios of 7.34 x 10(8) and 3.95 x 10(8), and subthreshold swing (SS) values of 0.23 and 0.19 V/decade, respectively. Therefore, proper annealing ambients contributed to internal modifications in the IGZO structure and led to an enhancement in the oxidation state of the metal. As a result, defects such as oxygen vacancies were eliminated. Oxygen annealing is thus effective for controlling the carrier concentration of the active layer, decreasing electron traps, and enhancing TFT performance.     

Preparation of pentacene thin film deposited using organic material auto-feeding system for the fabrication of organic thin film transistor

In this study, pentacene organic thin film was prepared using newly developed organic material auto-feeding system integrated with linear cell and characterized. The newly developed organic material auto-feeding system consists of 4 major parts: reservoir, micro auto-feeder, vaporizer, and linear cell. The deposition of organic thin film could be precisely controlled by adjusting feeding rate, main tube size, position and size of nozzle. 10 nm thick pentacene thin film prepared on glass substrate exhibited high uniformity of 3.46% which is higher than that of conventional evaporation method using point cell. The continuous deposition without replenishment of organic material can be performed over 144 hours with regulated deposition control. The grain size of pentacene film which affect to mobility of OTFT, was controlled as a function of the temperature.     

Organic thin film transistor using silver electrodes by the ink-jet printing technology

We have developed a conductive ink containing silver nanoparticles from which the electrodes for organic thin film transistor were directly patterned by ink-jet printing. Nano-sized silver particles having ∼ 20 nm diameter was used for a direct metal printing. Silver conductive ink was printed on the heavily doped n-type silicon wafer with 200-nm thick thermal SiO₂ layer as a substrate. To achieve a high line resolution and smooth conductive path, the printing conditions such as the inter-drop distance, stage moving velocity and temperature of the pre-heated substrates were optimized. After the heat-treatment at temperatures of 200 °C for 30 min, the printed silver patterns exhibit metal-like appearance and the conductivity. To fabricate a coplanar type TFTs, an active material of semiconducting oligomer, α,ω-dihexylquaterthiophene (DH4T) in a chlorobenzene was deposited between the ink-jet printed silver electrodes by drop casting. The OTFT with the ink-jetted source/drain electrodes shows general performance characteristics with good saturation behavior and no significant contact resistance as compared to the one with vacuum deposited electrodes. The electrical characteristic parameters of OTFT show the mobility of 1.3 × 10^− 3 cm² V^− 1 s^− 1 in the saturation regime, on/off current ratio over 10³, and threshold voltage of about − 13 V.     

The effect of hydrogen annealing on the molybdenum doped ZnO thin film

The electrical characteristics of hydrogen annealing on the molybdenum doped ZnO (MZO) thin film were discussed in the paper. The MZO film was deposited by an radio frequency sputtering, then it was annealed in hydrogen with a microwave plasma chemical vapor deposition system. The resistivity of MZO was decreased from 1.1 × 10^?2 to 9.5 × 10^?3 Ω cm after the hydrogen annealing. Improvements of the electrical properties are both due to the defects repairing through annealing and hydrogen doping effects of the MZO thin film. The higher temperature annealed MZO film shows slightly lower transmittance which is due to the higher carrier concentration.     

低电压并五苯晶体管的制北

介绍了利用物理气相沉积的技术制备有机物并五苯场效应晶体管(OTFT)的方法.通过扫描电镜(SEM)和X射线衍射谱(XRD)对并五苯薄膜的分析,发现并五苯薄膜具有良好的表面形貌和晶体特性.其载流子迁移率达0.3cm2/Vs,并五苯晶体管具有低电压特性.     

并五苯场效应晶体管的研制

以X射线衍射仪（XRD）研究了在硅表面形成并五苯多晶薄膜晶体结构，通过原子力显微镜（AFM）分析了在二氧化硅表面形成并五苯多晶薄膜的形貌。以热氧化的硅片作为绝缘栅极，并五苯作为有缘层，采用底接触结构，研制场效应晶体管。经过测试得到其场效应迁移率为1．23cm^2/Vs，开关电流比＞10^6。     

The development of a thin film transistor amplifier

An integrated amplifier has been designed to incorporate vacuum-deposited thin film field-effect transistors. An array of separate transistors was first produced to gain experience in manufacturing techniques and also to optimize the choice of electrode geometry and materials. A registration accuracy between layers of better than 5 μm was achieved by the use of a specially designed evaporator. The effects on the characteristics of water vapour and ion migration were largely eliminated by the complementary use of two transistors. The circuit had a midband gain of 20 db and a gain bandwidth product of approximately 500 kHz.     

The effect of annealing on amorphous indium gallium zinc oxide thin film transistors

This paper presents the post-annealing effects, caused by rapid thermal annealing (RTA), on amorphous indium gallium zinc oxide (a-IGZO) thin film transistor's (TFT) electrical characteristics, and its contact resistance (R_C) with thermally grown SiO₂ gate dielectric on silicon wafer substrates. The electrical characteristics of two types of TFTs, one post-annealed and the other not, are compared, and a simple model of the source and drain contacts is applied to estimate the R_C by a transmission line method (TLM). Consequently, it has been found that the post-annealing does improve the TFT performances; in other words, the saturation mobility (μ_sat), the on/off current ratio (I_ON/OFF), and the drain current (I_D) all increase, and the R_C and the threshold voltage (V_T) both decrease. As-fabricated TFTs have the following electrical characteristics; a saturation mobility (μ_sat) as large as 0.027 cm²/V s, I_ON/OFF of 10³, sub-threshold swing (SS) of 0.49 V/decade, V_T of 32.51 V, and R_C of 969 MΩ, and the annealed TFTs have improved electrical characteristics as follows; a μ_sat of 3.51 cm²/V s, I_ON/OFF of 10⁵, SS of 0.57 V/decade, V_T of 27.2 V, and R_C of 847 kΩ.     

Theory of the thin film transistor

A theoretical model for a polycrystalline film is proposed which takes account of the potential barriers at the intergrain boundaries and the band bending at the semiconductor/insulator interface. It is shown that a thin film transistor equation based on this model gives an improved fit with experiment compared with a model assuming no band bending at the interface. It is concluded that the device performance is dominated by the semiconductor/insulator interface.     

The effect of substrate temperature on Al-doped ZnO characteristics for organic thin film transistor applications

The influence of substrate temperature on the structural, electrical, and optical properties of aluminum-doped zinc oxide (AZO) films fabricated by radio frequency (RF) magnetron sputtering was investigated. The AZO films were deposited at various substrate temperatures, and the effect of AZO gate electrode conductivity on organic thin film transistor (OTFT) performance was examined. While an increase in the substrate temperature from 100 °C to 300 °C led to an improvement in crystallinity, substrate temperatures over 300 °C caused degradation of the electrical and surface properties. We fabricated OTFTs using AZO films prepared at various substrate temperatures and obtained good device performance. Thus, the performance of an OTFT can be determined by the conductivity of the AZO gate electrode.     

Investigating polysilicon thin film structural changes during rapid thermal annealing of a thin film crystalline silicon on glass solar cell

Structural changes resulting from rapid thermal annealing were investigated in a thin film crystalline silicon on textured glass solar cell, in particular grain parameters and film modulus. Electron backscatter diffraction showed no significant change in grain dimensions post annealing and no preferred orientation. Columnar grains with large defect densities were visible in transmission electron microscopy with no qualitative change visible post annealing. A similar modulus obtained by nanoindenation, both pre and post annealing suggests no quantitative structural change. The film structure appears unchanged by rapid thermal annealing.     

Ultraviolet light effect on electrical properties of a flexible organic thin film transistor

We have fabricated pentacene-based transistors on a transparent and flexible substrate made of polyethylene-terephthalate. We have shown that using an optical excitation at a wavelength of 365 nm photoconductivity modifies the carrier density without changing the mobility. The performance of the flexible organic phototransistors is mostly due to high-photosensitivity in the off-state with a ratio of photocurrent to dark current of about 2 10⁴. Furthermore, the response times of the phototransistor are lower than 0.1 s. These results indicate that such transistors could be potentially used in photodetectors or amplifiers ordered by an optical gate. Moreover, we have noticed that there is no significant change in the mobility value when the transistor is bent in the direction of the current flow.     

Transient charge accumulation in pentacene field effect transistor with silver electrode

Time-resolved microscopic optical second harmonic generation (TRM-SHG) imaging was employed to study a transient charge accumulation in top-contact pentacene field effect transistor (FET) with Ag electrodes. It was demonstrated that the SHG signal at the edge of the Ag electrode decayed but remained in a steady state depending on biasing condition. An electric field formed in pentacene layer below Ag electrode activates the SHG, indicating the insufficient accumulation of injected carriers in the FET channel. By using the TRM-SHG technique transient change of the carrier density in the OFET is obtained.     

热处理对金属薄膜压阻灵敏度的影响

采用磁控溅射法制备锰铜薄膜,溅射和真空蒸发法制备镱薄膜.对热处理前后薄膜的电学性能、微观形貌和结构进行了表征,并采用轻气炮和对顶砧装置对薄膜传感器进行了压阻性能测试,结果表明热处理后薄膜的压阻系数有很大提高.SEM和XRD的分析表明,压阻系数的提高是由于热处理后薄膜晶粒长大、缺陷减少、电阻率下降所致.敏感薄膜的电阻率与传感器的灵敏度直接相关.热处理后,薄膜压阻计的灵敏度已接近箔式传感器的水平,热处理是提高薄膜压阻计灵敏度的有效手段.     

Asymmetric fingered polysilicon p-channel thin film transistor structure for kink effect suppression

We present, for the first time, the application of the asymmetric fingered thin film transistor (AF-TFT) architecture to self-aligned p-channel TFTs for kink effect suppression. In AF-TFT the transistor channel region is split into two zones with different lengths (L₁ > L₂) separated by a floating p⁺ region. A fourth electrode, contacting the floating p⁺ region, allowed us to measure the individual electrical characteristics of the two sub-TFTs. Output characteristics show that substantial kink effect reduction can be achieved when the sub-TFT placed at the drain end of the device has an L₂ ? L₁. The electrical characteristics were analysed by using numerical simulations in the framework of the two-transistor model and we show that kink effect suppression arises from the operation in saturation regime of the source sub-TFT. The electrical characteristics of the fabricated p-channel AF-TFTs show a complete kink effect suppression, making these devices very attractive for current drivers in organic light emitting displays.     

Influence of illumination on the output characteristics in pentacene thin film transistors

The influence of illumination on the output characteristics of pentacene-based organic thin film transistors (OTFTs) was researched in this study. It is shown that light illumination may lead to an increase in the drain current, shifting the threshold voltage towards positive gate–source voltages. This is because of the light-induced acceptor activation, which is a new concept for illumination-dependent output characteristics of OTFTs. However, the field-effect mobility is insensitive to light illumination. It is found that electron trapping is responsible for the experimentally observed illumination-dependent output behavior of charge transport in OTFTs.