Surface state electrons on a hydrogen film. 2. Influence of adsorbed helium films

We have investigated the conductivity of surface state electrons on liquid⁴He films supported by a quench-condensed thin solid hydrogen substrate. A pronounced dip in the ac-conductivity was observed as the He film thickness reached about 10 layers. This phenomenon was studied at different temperatures (range between 1.6 and 2 K), electron densities from 0.9 to 19×10⁸ cm^–2, frequencies between 1 and 100 kHz, and for various amplitudes of the ac driving voltage. Ripplon scattering and a ripplonic polaron are discussed as sources for the conductivity dip.     

Possible correlation effects of surface state electrons on a solid hydrogen film

We have investigated the transport properties of surface state electrons on thin quench-condensed hydrogen films for various electron densities. The surface state electron mobility showed a continuous dependence on the plasma parameter in the range from 20 to 130, indicating a strong influence of correlation effects within the electron system for all measured values of .     

Energy distributions of electrons emitted from a diamond film under the action of a strong field

Results are presented of measurements of the total energy distributions of electrons emitted under the action of a strong external field from the surface of a thin diamond-like film, fabricated by ion-beam deposition on a tungsten tip. The data confirm that carriers are injected into the conduction band of the film and then emitted into vacuum. Pis’ma Zh. Tekh. Fiz. 25, 46–52 (August 12, 1999)     

Kapton/Al薄膜的电子辐照损伤

使用空间综合辐照设备对Kapton/Al薄膜进行了电子辐照的地面模拟实验,研究了Kapton薄膜的表面形貌、光学性能变化和辐照损伤机制.结果表明,辐照使Kapton薄膜表面发生了明显的充放电效应;在500-1000 nm波长区间光谱反射系数明显降低,太阳吸收比随着电子辐照剂量的增加而增高;在辐照过程中Kapton薄膜发生酰亚胺基团的破坏、羰基和桥氧键的断裂以及O在N 逸出空位处的替换,并有较复杂的新结构生成.     

退火温度对RF磁控溅射ZnO薄膜力学性能的影响

采用X射线衍射分析(XRD),原子力显微镜(AFM)及纳米压痕技术测试分析了多晶ZnO薄膜的晶格结构和力学性能.薄膜的制备采用了射频(RF)磁控溅射方法,并分别在不同温度下进行了退火处理.XRD分析显示随着退火温度的上升,薄膜的晶粒尺寸逐步增大,且C轴取向显著增强.压痕测试结果表明,由于尺寸效应的影响,硬度随退火温度的变化有明显的趋势,从2.5GPa(常温下)逐步增加到5.5GPa(4500C),随着温度的进一步上升,硬度值又逐步下降到4.5GPa(650℃).弹性模量整体随退火温度的变化并不呈现明显的规律,但在450℃和200℃下退火分别有最大值26.7GPa和最小值21.5GPa,这是由于尺寸效应与晶格取向的双重作用的结果.测试结果表明适当的退火处理对ZnO薄膜的结晶品质与力学性能有明显的改善.     

Peculiarities of film growth in glow discharge with runaway electrons

We have studied the properties of films deposited in gas discharge with a beam of runaway electrons and observed for the first time an anomalous behavior of the intensity of a probing light beam reflected from a film on substrate upon switching off of the discharge. The observed phenomenon is interpreted in the framework of a two-layer model of the film growth on a substrate, according to which an optically homogeneous surface layer of unknown nature appears on the film during growth in discharge and fully decomposes when the discharge is switched off.     

Annealing optimization of silicon nitride film for solar cell application

Hydrogenated films of silicon nitride (SiNx:H) is commonly used as an antireflection coating as well as passivation layer in crystalline silicon solar cell. SiNx:H films deposited at different conditions in Plasma Enhanced Chemical Vapor Deposition (PECVD) reactor were investigated by varying annealing condition in infrared (IR) heated belt furnace to find the optimized condition for the application in silicon solar cells. By varying the gases ratio (R = NH₃/SiH₄ + NH₃) during deposition, the SiNx:H films of refractive indices 1.85-2.45 were obtained. Despite the poor deposition rate, the silicon wafer with SiNx:H film deposited at 450 °C showed the best effective minority carrier lifetime. The film deposited with the gases ratio of 0.57 shows the best peak of carrier lifetime at the annealing temperature of 800 °C. The single crystalline silicon solar cells fabricated in conventional industrial production line applying the optimized film deposition and annealing conditions on large area substrates (125 mm × 125 mm) were found to have the conversion efficiencies as high as 17.05 %. Low cost and high efficiency single crystalline silicon solar cells fabrication sequence employed in this study has also been reported in this paper.     

The effect of hydrogen on the conductivity of Ag-Pd thick film resistors

The resistance of silver-palladium thick film resistors decreases and their surface conduction type changes upon heating in a flow of hydrogen at temperatures within 50–100°C or hydrogenation in an aqueous acid electrolyte at room temperature. These effects are due to the reduction of PdO (present in the Ag-Pd film) to Pd by hydrogen entering into the resistor material. In the electrolyte, the resistance of samples starts decreasing at the moment of the current being switched on.     

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.     

质子、电子综合辐照作用下Teflon FEP/Al辐照损伤效应研究

在地面模拟研究了能量为30keV的质子与电子辐照对Teflon FEP/Al的光学性能退化的综合影响。结果表明,质子辐照引起Teflon FEP/Al在可见光区反射性能退化,而电子引起其在可见光与近红外区反射性能的全面下降。电子辐照更多的是使材料的大分子形成激发态进而轰击出主链上的F原子,形成自由基以及游离态的C。质子辐照时,除产生上述的辐照缺陷外,H~*的离子注入还使材料中形成各种新的官能团。质子与电子辐照的顺序不同,Teflon FEP/Al的C_(1s)谱也明显不同。     

Escape rate of two-dimensional electrons on a liquid helium surface around 1 K

Electron escape from a two-dimensional surface state on liquid helium to three-dimensional free space is studied. A thermal-activation-type temperature dependence of the escape rate is observed at 1.1>T>0.9 K for the first time. The mechanism of electron escape is discussed.     

Effects of the hydrogen content on the development of anodic aluminum oxide film on pure aluminum

In this study, high purity aluminum (Al) samples containing different levels of hydrogen were used as a base metal for anodization. To ensure constant current densities during the experiments, the voltage-time (V-t) curves were recorded. The differential ΔV/Δt curves were plotted and the energy consumed during different steps of anodization was calculated. Experimental observations show that differences in the hydrogen content affected the amount of energy consumed. The process was divided into three steps.When the voltage response at the end of step 2 exceeded 25 V, the energy consumed in steps 2 + 3 reached or exceeded 7.4 J/cm², and the pore channels branched or merged, creating a spike in the ΔV/Δt curves in step 3. A combination of the effects of the high voltage response at the end of step 2 and the high hydrogen content in the Al samples led to the formation of an anodic aluminum oxide (AAO) film in the sulfuric acid solution, which produced crystallized boehmite. This study proposes a unique tool for understanding certain special anodic behaviors of pure Al, wherein the branching or merging of pore channels and the partial crystallization of the AAO film can be ascertained by looking at the irregularities in the ΔV/Δt curves obtained in step 3.     

New hydrogen sensor based on sputtered Mg-Ni alloy thin film

Pd-capped magnesium-nickel alloy thin films were prepared by magnetron sputtering and their hydrogen sensing properties were investigated. By monitoring the resistance change or the transmittance change of the film, we can obtain the information on hydrogen concentration in air. The sensing range of this sensor is quite wide and it can measure the hydrogen concentration range from 10 ppm to 10% without heating. Using a certain protective coating, the durability of the film can be much improved. Also there is a unique application of Pd/Mg-Ni thin film as ‘hydrogen check sheet’, which can visualize the hydrogen flow.     

Investigation of electrons localized above solid hydrogen by means of the cyclotron resonance method

The magnetoresistance and cyclotron resonance of a two-dimensional sheet of electrons localized above liquid and solid hydrogen surfaces are investigated at the frequency of 20 GHz. It is found that the effective electron mass relevant to the motion along the surface is close to the free electron mass. The electron mean free path is determined by collisions with defects of the solid hydrogen surface. For 5?T?12 K the electron mobility was ～8×10⁴/T cm²/V sec, with 20% accuracy, for all the specimens investigated. ForT?5 K the mobility follows the law \(\mu \propto 1/\sqrt {{\text{W}}_{\text{e}} } \) , wherew _e is the mean electron energy. The numerical values of the electron mobilities for different specimens differ by factors up to five, and forT?1 K they fall within within the range 2×10⁴ to 10⁵ cm²/V sec. The experimental results indicate that the solid hydrogen surface has a terrace structure with flat sections about 10^?5 cm in size. During the investigation of electrons localized above a saturated helium film wetting the solid hydrogen, we observed a shift of the resonance to weaker magnetic fields, which amounts to ～100% at a pressing field of ～10³ V/cm. It is shown that this shift can be explained by the terrace structure of the substrate.     

Effect of film thickness on hydrogen content in a-Si : H

The hydrogen content, its depth distribution, and its bonding configuration have been studied in hydrogenated amorphous silicon prepared by plasma-enhanced chemical vapor deposition with hydrogen-diluted silane. Nuclear reaction analysis and infrared spectroscopy were used to determine the total amount of hydrogen and its bonded component, respectively. It has been established that the total concentration of hydrogen does not depend on the film thickness, and has a uniform depth profile. The concentration of bonded hydrogen changes with the film thickness within the measurement accuracy. The data obtained suggest the presence of molecular (non-bonded) hydrogen, uniformly distributed in concentration across the film thickness.