An ac microcalorimeter for measuring specific heat of thin films

Microcalorimeter based on suspended SiO₂ membrane structures has been designed and fabricated. The geometry of suspension arms is optimized by ANSYS simulation to ensure that it provides maximum thermal isolation between the membrane structure and the supporting substrate. The microcalorimeter is intended to be a sample carrier onto which other thin films can be deposited for thermal property measurement. An ac modulation method has been used to measure the specific heat of aluminum thin film with thickness from 13.5 to 370 nm. The measurements demonstrated clearly the dependence of specific heat on thin film thickness.     

Simple method of measuring drift-mobility profiles in thin semiconductor films

A simple method of measuring drift-mobility profiles in semiconductor films is described. It is based on the low-frequency measurement of the transconductance and gate capacitance of an f.e.t. structure as a function of gate bias. Drift mobilities of 4000 to 5000 cm2/Vs have been measured on n-type GaAs films with 1016 to 1017 cm?3 doping levels.     

Control of magnetostatic waves in thin films by means of spatially nonuniform bias fields

Although magnetostatic wave devices normally employ spatially uniform magnetic bias, control of important features of the modes is afforded through judicious use of dc field gradients. Such control can be the basis for new forms of microwave signal processors.Gradients in either the field magnitude, direction, or both can be employed to affect wave dispersion or mode spectra. This is done to control prespecified characteristics such as frequency, rf energy distribution, impedance, and the velocity of energy propagation.Very general mathematical analyses of both the forward volume wave and surface wave geometries are developed for cases where the effective magnetic bias has, depending upon the mode, transverse spatial variation along either the ferrite film width or thickness caused by the applied field, saturation magnetization, magnetic anisotropy — or some combination.Computer simulation has been used to obtain eigenfrequencies and eigenmodes when the bias is uniform or nonuniform. The latter cases reveal that a great deal of control over the mode energy distributions can be exercised by the proper choice of gradients. For example, a forward volume wave can be forced to have strong field-displacement characteristics that are either nearly reciprocal or very strongly nonreciprocal.This research was supported, in part, by the Joint Services Electronic Program (JSEP) under Contract DAAG29-83-K-0003 administered by the Research Laboratory of Electronics (RLE); the National Science Foundation under Grant 8008628-DAR; and STAS 0356 administered by the Battelle Research Triangle Park Office.     

Synthesis of highly conductive cobalt thin films by LCVD at atmospheric pressure

We have deposited very low resistant Co films on SiO₂-coated Si substrates using UV pulsed laser pyrolytic decomposition of Co₂(CO)₈ with 355 nm laser radiation at atmospheric pressure. Facile decomposition of the precursors and the use of Ar curtain enable the deposition of relatively pure Co (with O less than 7% and negligible C) at the power of 1.11–3.33 W, and of pure Co at 6.67 W. The resistivity decreases from 58 to 19 µΩ-cm as the power increases from 2.22 to 3.33 W, showing inverse-linear dependence on grain size. In addition, further increase of the power to 6.67 W decreases the resistivity to 9 µΩ-cm, due to both the growth of large grains with negligible contaminants, and the adverse effect of surface roughness. The effects of oxygen contaminants on the resistivity can be minimal, because of its presence in the form of oxide. These low resistant fine metal lines deposited by a direct-writing laser chemical vapor deposition technique at atmospheric pressure have been reported for the first time.     

一种用于薄膜热容测量的微热量计的设计与制作

目前已发现并证实薄膜的热导率和热扩散率存在着尺寸效应。本文为了研究薄膜的另一个热学性质比热是否也具有尺寸效应,提出了一种用于薄膜热容测量的新方法,其相应的实验器件为一悬膜结构。从理论上阐述了其测量原理,结合ANSYS热学模拟设计并利用微机械加工技术制作出SiO2悬膜结构,悬膜由两个悬臂支撑,在悬膜上制作了Pt薄膜电阻同时用于加热和测温。这种结构加快了样品、悬膜和加热/测温电阻之间的热传递,减小了悬膜的热损失,提高了测量精度。     

一种用于薄膜热容测量的微热量计的设计与制作

目前已发现并证实薄膜的热导率和热扩散率存在着尺寸效应。本文为了研究薄膜的另一个热学性质比热是否也具有尺寸效应 ,提出了一种用于薄膜热容测量的新方法 ,其相应的实验器件为一悬膜结构。从理论上阐述了其测量原理 ,结合ANSYS热学模拟设计并利用微机械加工技术制作出SiO2 悬膜结构 ,悬膜由两个悬臂支撑 ,在悬膜上制作了Pt薄膜电阻同时用于加热和测温。这种结构加快了样品、悬膜和加热 /测温电阻之间的热传递 ,减小了悬膜的热损失 ,提高了测量精度。     

用透射光谱和模拟退火算法确定薄膜光学常数

提出了用透射光谱曲线和模拟退火算法同时确定薄膜材料折射率n、消光系数k及薄膜厚度d的方法,并给出了严格的理论公式和计算程序框架图。为了验证此方法的准确性和可行性,先进行了计算模拟,然后对SiNx薄膜进行了测量。模拟结果与理论值非常接近,根据实验结果恢复出来的曲线与原始实验曲线吻合得很好。此方法具有非破坏性、测量简单、操作方便、稳定性好和计算收敛速度快、精度高等特点。     

Anomalous thermal oxidation of gadolinium thin films deposited on silicon by high pressure sputtering

Thin gadolinium metallic layers were deposited by high-pressure sputtering in pure Ar atmosphere. Subsequently, in situ thermal oxidation was performed at temperatures ranging from 150 to 750 °C. At an oxidation temperature of 500 °C the films show a transition from monoclinic structure to a mixture of monoclinic and cubic. Regrowth of interfacial SiO_x is observed as temperature is increased, up to 1.6 nm for 750 °C. This temperature yields the lowest interface trap density, 4 × 10¹⁰ eV⁻¹ cm⁻², but the effective permittivity of the resulting dielectric is only 7.4. The reason of this low value is found on the oxidation mechanism, which yields a surface with located bumps. These bumps increase the average thickness, thus reducing the capacitance and therefore the calculated permittivity.     

利用多站址场强幅度测量法实现无线电定位

在城市环境中,确定干扰源位置通常是采用固定测向与移动测向相结合的方法。即先用固定测向定位的方法将干扰源确定在一个较小的范围内,然后再用移动测向的方法确定干扰源的具体位置。由于固定测向站的设备比较复杂、价格昂贵且须多站同时交绘定向才能完成定位,同时固定测向站对天线和天线场地的要求也比较高。本文对一种比较简便的采用 全向天线和普通接收机实现无线电定位的方法（仅就VHF、UHF频段）。 由电波传播规律可知,电波发射源周围场强随着与发射源距离的增加而递减。下面以一个实例来分析这种关系。 如果在一未知电波发射源…     

氧压对PLD制备掺铜ZnO薄膜光学性质的影响

为了研究生长氧压对ZnO薄膜的结构和光学性质的影响,采用脉冲激光沉积技术,在P-Si〈111〉衬底上制备了不同生长氧压下的掺铜ZnO薄膜.利用X射线衍射仪对样品的结构进行了分析,并用荧光分光光度计对样品的光致发光谱进行了测量.结果表明,所有样品均在2θ=34.3°附近出现ZnO(002)衍射峰,没有发现Cu的衍射峰,在...     

Electromigration in electroplated Cu(Ag) alloy thin films investigated by means of single damascene Blech structures

Electromigration failure of copper interconnects in microelectronics evokes a need for materials with improved resistance against electromigration effects. Copper–silver alloy thin films are a promising material for the next generation of interconnects and were investigated with respect to their electromigration resistance. The investigations were done by atom drift experiments by means of Blech structures fabricated in single damascene technology with two different Ta-based liner systems. Electromigration induced atom drift could be demonstrated. The resistance against electromigration of Cu(Ag) films appears to be slightly higher than for pure Cu films. However, significant experimental errors are still present. Additionally, de-alloying effects were observed.     

Structural properties of FeTe2 thin films synthesized by tellurization of amorphous iron oxide thin films

This paper deals with the structural properties of FeTe₂ thin films obtained using a simple and non-toxic experimental procedure. First, iron oxide thin films have been prepared by the spray pyrolysis technique from an aqueous solution containing FeCl₃6H₂O (0.03 M) as a precursor onto glass substrates heated at 623 K. Second, these films were subjected to a heat treatment under tellurium atmosphere at various temperatures (723–803 K) for 24 h. XRD analysis revealed that FeTe₂-ortorombic phase films were obtained at a heat treatment of the order of 773 K. This film has a good crystalline state with a preferential orientation of the crystallites along (111) direction. Moreover, AFM as well as SEM morphological observations show a relatively perturbed surface state.To date, this simple and low cost route process to obtained FeTe₂ thin films has not yet been used.     

Optical response of tin nitride thin films prepared by halide chemical vapor deposition under atmospheric pressure

Optical response of tin nitride (SnN_x) films, which were deposited onto quartz substrates by means of atmospheric pressure, halide chemical vapor deposition (AP-HCVD), were examined by pulsed irradiation of a YAG laser (532 nm). It was observed that the transmittance of a light of a He-Ne laser (633 nm) through the SnN_x film decreases after the film is irradiated with a YAG laser. The atomic force microscopy (AFM) micrograph observation confirmed that spot-like humps appeared on the SnN_x film surface in the regions spotted by the YAG laser. This phenomenon was explained in terms of the laser-assisted thermal decomposition of SnN_x to β-tin.     

共蒸发方法制备GaSb多晶薄膜

We report optical and electrical properties of polycrystalline GaSb thin films which were successfully grown by co-evaporation on soda-lime glass substrates. The thin films have preferential orientation of the （111） direction. SEM results indicate that the average grain size of GaSb thin film is 500 nm with the substrate temperature of 560 ℃. The average reflectance of GaSb thin film is about 30% and the absorption coefficient is of the order of 10^4 cm^-1. The optical bandgap of GaSb thin film is 0.726 eV. The hole concentration shows a clear increasing trend as the Ga-evaporation-temperature/Sb-evaporation-temperature （TGa/Tsb） ratio increases. When the Ga crucible temperature is 810 ℃ and the antinomy crucible temperature is 415 ℃, the hole concentration of polycrystalline GaSb is 2 × 10^17 cm^-3 and the hole mobility is 130 cm^2/（V·s）. These results suggest that polycrystalline GaSb thin film is a good candidate for the use as a cheap material in TPV cells.     

Polycrystalline GaSb thin films grown by co-evaporation

We report optical and electrical properties of polycrystalline GaSb thin films which were successfully grown by co-evaporation on soda-lime glass substrates. The thin films have preferential orientation of the (111)direction. SEM results indicate that the average grain size of GaSb thin film is 500 nm with the substrate temperature of 560 ℃. The average reflectance of GaSb thin film is about 30% and the absorption coefficient is of the order of 104 cm-1. The optical bandgap of GaSb thin film is 0.726 eV. The hole concentration shows a clear increasing trend as the Ga-evaporation-temperature/Sb-evaporation-temperature (TGa/TSb) ratio increases. When the Ga crucible temperature is 810 ℃ and the antinomy crucible temperature is 415 ℃, the hole concentration of polycrystalline GaSb is 2 x 1017 cm-3 and the hole mobility is 130 cm2/(V-s). These results suggest that polycrystalline GaSb thin film is a good candidate for the use as a cheap material in TPV cells.     

应用高压高功率的微晶硅薄膜高速沉积

应用高压高功率(hphP)甚高频等离子增强化学气相沉积(VHF-PECVD)法对微晶硅(μc-Si:H)进行高速沉积,确定了hphP VHF-PECVD法沉积μc-Si:H的最优条件参数,在此参数下对hphP和低压低功率(IplP)两组样品沉积速率、光电导、暗电导及光敏性等性能参数进行测试,得到了1.58 nm的较高沉...     

水热—溶胶凝胶法制备PZT薄膜

采用水热—溶胶凝肢法制备了锆钛酸铅( PZT)压电陶瓷薄膜.首先利用水热法处理Si基板,使之生成SiO2/Si层,然后采用旋涂法在处理好的Si基板上涂覆摩尔比r(Zr:Ti)为52:48的PZT前驱体溶胶.研究了基板处理方式、退火温度以及涂胶层数对PZT薄膜结晶性能、表面形貌及厚度的影响.结果表明:水热处理Si基板对P...     

PECVD制备纳米晶多晶硅薄膜

以Si(100)为衬底,采用磁控溅射和射频等离子体增强化学气相沉积系统制备了Si(100)/Al膜/非晶Si膜结构的样品。对该样品进行Al诱导真空退火以制备多晶硅薄膜,采用X射线衍射仪(XRD)和AFM分析薄膜微结构及表面形貌。实验结果表明,在经过500℃、550℃Al诱导退火后,形成了择优取向为〈111〉晶向的多晶硅薄膜。AFM给出了550℃退火后薄膜表面形貌,为100～200nm大小的圆丘状硅晶粒,密集排列在薄膜表面;并对Al诱导真空退火晶化的机理进行了分析。