APCVD生长碳化硅薄膜中汽相结晶过程的研究

对宽禁带半导体材料碳化硅薄膜的常压化学汽相沉积(APCVD)异质外延技术进行了讨论.在SiC薄膜的生长过程中对Si/C原子比例的控制一直是影响薄膜表面形貌和膜层掺杂浓度的重要因素.针对水平卧式反应室,分析了生长过程中气流流速分布、反应室内温度分布以及反应气体浓度分布,指出"汽相结晶"过程对薄膜生长区Si/C比例有很大影响,从而影响了碳化硅薄膜的生长速率,非常好的解释了薄膜生长过程中出现的现象.     

Al(001)表面上沉积Ti薄膜的分子动力学模拟

采用分子动力学模拟方法,研究了Ti原子连续沉积于Al(001)表面上的薄膜生长过程,分析了入射能量为0.1、5 eV和衬底温度为300、700 K时的界面结合及微观结构.模拟结果表明,增加入射能量和衬底温度,使Ti薄膜的表面越光滑;通过径向分布函数和键对分析技术对薄膜微观结构进行分析,发现衬底温度时薄膜微观结构影响较大,温度300 K及以下时,Ti薄膜主要是FCC结构,随着温度升高,FCC结构成分减少,无序结构成分增加,而入射能量则对薄膜微观结构没有明显影响.     

SiO2/Si衬底上石墨烯的制备与结构表征

在分子束外延(MBE)设备中,利用直接沉积C原子的方法在覆盖有SiO₂的Si衬底(SiO₂/Si)上生长石墨烯,并通过Raman光谱和近边X射线吸收精细结构谱等实验技术对不同衬底温度(500℃,600℃,700℃,900℃,1100℃,1200℃)生长的薄膜进行结构表征.实验结果表明,在衬底温度较低时生长的薄膜是无定形碳,在衬底温度高于700℃时薄膜具有石墨烯的特征,而且石墨烯的结晶质量随着衬底温度的升高而改善,但过高的衬底温度会使石墨烯质量降低.衬底温度为1100℃时结晶质量最好.衬底温度较低时C原子活性较低,难以形成有序的C-sp²六方环.而衬底温度过高时(1200℃),衬底表面部分SiO₂分解,C原子与表面的Si原子或者O原子结合而阻止石墨烯的形成,并产生表面缺陷导致石墨烯结晶变差.     

动力学晶格蒙特卡洛方法模拟Cu薄膜生长

利用动力学晶格蒙特卡洛方法模拟了Cu薄膜在Cu(100)面上的三维生长过程。模型中考虑了四个动力学过程:原子沉积、增原子迁移、双原子迁移和台阶边缘原子迁移,各动力学过程发生的概率由多体势函数确定。讨论了基底温度、沉积速率及原子覆盖率对Cu原子迁移、成核和表面岛生长等微观生长机制的影响;获得了Cu薄膜的表面形貌图并计算了表面粗糙度。模拟结果表明,随基底温度升高或沉积速率下降,岛的平均尺寸增大,数目减少,形状更加规则。低温时,Cu薄膜表现为分形的离散生长,高温时,Cu原子迁移能力增强形成密集的岛。Cu薄膜表面粗糙度随着基底温度的升高而迅速减小;当基底温度低于某一临界温度时,表面粗糙度随原子覆盖率或沉积速率的增大而增大;当基底温度超过临界温度时,表面粗糙度随原子覆盖率或沉积速率的变化很小,基本趋于稳定。     

Si表面离子束辅助沉积Ti纳米膜的研究

用离子束技术探讨了Si表面纳米Ti薄膜制备的可行性以及Ti薄膜组织结构与离子束工艺之间的关系。实验进行试样表面预处理、轰击离子能量、离子密度、温度、沉积时间等离子束工艺参数对单晶Si(111)表面沉积的Ti薄膜结构的影响。采用原子力显微镜(AFM)和扫描电子显微镜(SEM)分析了Ti膜表面晶粒形貌，并用X射线衍射仪(XRD)和俄歇电子谱仪(AES)分析了Ti膜的结构和成分。由于残余气体的影响，Ti膜发生了不同程度的氧化，随温度升高和轰击离子强度增加氧化愈加明显。     

Growth Kinetics of Silicon Carbide Film Prepared by HeatingPolystyrene/Si(111)

在不同的温度下热处理用sol-gel法制的PS/Si(111)叠层凝胶膜制备出了SiC薄膜．用XRD、SEM、XPS、FTIR等分析方法研究了SiC薄膜的结构、组成和表面形貌等．根据FTIR光谱计算了不同温度下得到的SiC薄膜的厚度,并研究了PS/Si(111)热解法生长SiC薄膜的生长动力学．结果表明,随着生长温度的增加,SiC薄膜生长速率变化趋势为：1200～1250 oC生长速率增加缓慢是2D生长机制,1250～1270 oC生长速率快速增加是3D生长机制,1270～1300 oC生长速率为负增长是由于SiC薄膜生长与Si和C原子的挥发共同作用所致．由速率变化求得各段表观生长激活能分别是122.5、522.5、-127.5 J/mol．     

载能原子沉积Au/Au(100)外延薄膜生长的计算机模拟

在分子动力学研究的基础上建立了载能原子的沉积动力学物理模型,并根据在局域环境下的表面原子扩散模型,通过运动学Monte Carlo方法研究了载能粒子沉积Au/Au(100)薄膜的初期生长过程,探讨了载能粒子沉积对薄膜生长的影响及其随基体温度的变化.通过计算机模拟发现：载能粒子沉积的Au/Au(100)薄膜生长仍然呈现层状生长-三维岛状生长-准二维层状.在薄膜生长初期,载能粒子的作用是促进表面原子的成核,增加基体表面的缺陷;在薄膜的生长阶段,载能粒子通过抑制三维岛的生长速率起着平滑薄膜表面形貌的作用.载能粒 关键词：     

等离子增强原子层沉积低温生长GaN薄膜

采用等离子增强原子层沉积技术在低温下于单晶硅衬底上成功生长了Ga N多晶薄膜,利用椭圆偏振仪、低角度掠入射X射线衍射仪、X射线光电子能谱仪对薄膜样品的生长速率、晶体结构及薄膜成分进行了表征和分析.结果表明,等离子增强原子层沉积技术生长Ga N的温度窗口为210—270?C,薄膜在较高生长温度下呈多晶态,在较低温度下呈非晶态;薄膜中N元素与大部分Ga元素结合成N—Ga键生成Ga N,有少量的Ga元素以Ga—O键存在,多晶Ga N薄膜含有少量非晶态Ga_2O_3.     

螺旋波等离子体增强化学气相沉积氮化硅薄膜

利用螺旋波等离子体增强化学气相沉积(HWP-CVD)技术，以SiH4和N2为反应气体进行了氮化硅(SiN)薄膜沉积，并研究了实验参量对薄膜特性的影响.利用傅里叶变换红外光谱、紫外—可见光谱和椭偏光检测等技术对薄膜的结构、厚度和折射率等参量进行了测量.结果表明，采用HWP-CVD技术能在低衬底温度条件下以较高的沉积速率制备低H含量的SiN薄膜，所沉积的薄膜主要表现为Si—N键合结构.采用较低的反应气体压强将提高薄膜沉积速率，并使薄膜的致密性增加.适当提高N2/SiH4比例有利于薄膜中H含量的降低. 关键词： 螺旋波等离子体 化学气相沉积 氮化硅薄膜     

Si基Bi4Ti3O12铁电薄膜的制备与特性研究

采用sol-gel工艺,在分层快速退火的工艺条件下成功地制备了高质量Si基BiTi3O12铁电薄膜.研究了Si基Bi4Ti3O12薄膜的生长行为、铁电性能、C-V特性和疲劳特性.研究表明:Si基Bi4Ti3O12薄膜具有随退火温度升高沿c轴择优生长的趋势;退火温度通过影响薄膜的晶粒尺寸、生长取向和薄膜中载流子的浓度来改变Si基Bi4Ti3O12薄膜的铁电性能;Ag/Bi4Ti3O12/p-Si异质结的C-V特性曲线呈现顺时针回滞,可以实现极化存储;109次极化反转后Bi4Ti3O12薄膜的剩余极化仅下降12%,具有较好的疲劳特性.     

Formation of Ti1–x Si x and Ti1–x Si x N films by magnetron co-sputtering

The paper reports on surface morphology, structure and microhardness of TiSi–N films formed by cosputtering from two target-facing unbalanced magnetrons, equipped with pure Ti and Si targets, on an unheated substrate rotating in front of both targets. The ratio Si/Ti in the TiSi–N film was achieved by modifying the magnitude of currents in the individual magnetrons and by the addition of nitrogen to the film. The rotation of the substrate has a strong effect on the film deposition rate and its morphology. The deposition rate is 3 times lower than that of the film deposited on a stationary substrate. The surface roughness of a polycrystalline Ti film deposited on the rotating substrate is considerably higher than that on a stationary substrate. On the contrary, the surface of an amorphous Si film is smooth and there is no difference between the roughness of Si films sputtered on stationary and on rotating substrates. The hardness of the film increases with increasing Si content and with the addition of nitrogen to the TiSi film. The Ti(26 at.%)Si(8.5 at.%)N(65 at.%)-film sputtered on an unheated rotating steel substrate, held at a floating potential, exhibited the best result with a hardness of 29 GPa.     

The influence of substrate temperature variation on tungsten oxide thin film growth in an HFCVD system

Tungsten oxide (WO₃) thin films were deposited by a modified hot filament chemical vapor deposition (HFCVD) technique using Si (1 0 0) substrates. The substrate temperature was varied from room temperature to 430 °C at an interval of 100 °C. The influence of the substrate temperature on the structural and optical properties of the WO₃ films was studied. X-ray diffraction and Raman spectra show that as substrate temperature increases the film tends to crystallize from the amorphous state and the surface roughness decreases sharply after 230 °C as confirmed from AFM image analysis. Also from the X-ray analysis it is evident that the substrate orientation plays a key role in growth. There is a sharp peak for samples on Si substrate due to texturing. The film thickness also decreases as substrate temperature increases. UV-vis spectra show that as substrate temperature increases the film property changes from metallic to insulating behavior due to changing stoichiometry, which was confirmed by XPS analysis.     

Effect of temperature on residual stress and mechanical properties of Ti films prepared by both ion implantation and ion beam assisted deposition

Ti films with a thickness of 1.6 μm (group A) and 4.6 μm (group B) were prepared on surface of silicon crystal by metal vapor vacuum arc (MEVVA) ion implantation combined with ion beam assisted deposition (IBAD). Different anneal temperatures ranging from 100 to 500 °C were used to investigate effect of temperature on residual stress and mechanical properties of the Ti films. X-ray diffraction (XRD) was used to measure residual stress of the Ti films. The morphology, depth profile, roughness, nanohardness, and modulus of the Ti films were measured by scanning electron microscopy (SEM), scanning Auger nanoprobe (SAN), atomic force microscopy (AFM), and nanoindentation, respectively. The experimental results suggest that residual stress was sensitive to film thickness and anneal temperature. The critical temperatures of the sample groups A and B that residual stress changed from compressive to tensile were 404 and 428 °C, respectively. The mean surface roughness and grain size of the annealed Ti films increased with increasing anneal temperature. The values of nanohardness and modulus of the Ti films reached their maximum values near the surface, then, reached corresponding values with increasing depth of the indentation. The mechanism of stress relaxation of the Ti films is discussed in terms of re-crystallization and difference of coefficient of thermal expansion between Ti film and Si substrate.     

Molecular dynamics and experimental studies on deposition mechanisms of ion beam sputtering

Molecular dynamics (MD) simulation and experimental methods are used to study the deposition mechanism of ionic beam sputtering (IBS), including the effects of incident energy, incident angle and deposition temperature on the growth process of nickel nanofilms. According to the simulation, the results showed that increasing the temperature of substrate decreases the surface roughness, average grain size and density. Increasing the incident angle increases the surface roughness and the average grain size of thin film, while decreasing its density. In addition, increasing the incident energy decreases the surface roughness and the average grain size of thin film, while increasing its density. For the cases of simulation, with the substrate temperature of 500 K, normal incident angle and 14.6 × 10⁻¹⁷ J are appropriate, in order to obtain a smoother surface, a small grain size and a higher density of thin film. From the experimental results, the surface roughness of thin film deposited on the substrates of Si(1 0 0) and indium tin oxide (ITO) decreases with the increasing sputtering power, while the thickness of thin film shows an approximately linear increase with the increase of sputtering power.     

Kinetic Monte Carlo simulation of thin film growth

A three-dimensional kinetic Monte Carlo technique has been developed for simulating growth of thin Cu films. The model involves incident atom attachment, diffusion of the atoms on the growing surface, and detachment of the atoms from the growing surface. The related effect by surface atom diffusion was taken into account. A great improvement was made on calculation of the activation energy for atom diffusion based on a reasonable assumtion of interaction potential between atoms. The surface roughness and the relative density of the films were simulated as the functions of growth substrate temperature and film thickness. The results showed that there exists an optimum growth temperatureT _opt at a given deposition rate. When the substrate temperature approaches toT _opt, the growing surface becomes smoothing and the relative density of the films increases. The surface roughness minimizes and the relative density saturates atT _opt. The surface roughness increases with an increment of substrate, temperature when the temperature is higher thanT _opt.T _opt is a function of the deposition rate and the influence of the deposition rate on the surface roughness depends on the substrate temperatures. The simulation results also showed that the relative density decreases with the increasing of the deposition rate and the average thickness of the film.     

衬底温度对PLD制备的Mo薄膜结构及表面形貌的影响

 运用脉冲激光沉积(PLD)技术在Si(100)基片上沉积了金属Mo薄膜。在激光重复频率2 Hz,能量密度5.2 J/cm²,本底真空10^－6 Pa的条件下,研究Mo薄膜的结构和表面形貌,讨论了衬底温度对薄膜形貌与结构的影响。原子力显微镜(AFM)图像和X射线小角衍射(XRD)分析表明,薄膜表面平整、光滑,均方根粗糙度小于2 nm。沉积温度对Mo薄膜结构和表面形貌影响较大,在373~573 K范围内随着温度升高,薄膜粗糙度变小,结晶程度变好。     

Electronic structure and defect states of transition films from amorphous to microcrystalline silicon studied by surface photovoltage spectroscopy

In this paper, surface photovoltage spectroscopy (SPS) is used to determine the electronic structure of the hydrogenated transition Si films. All samples are prepared by using helicon wave plasma-enhanced chemical vapour deposition technique, the films exhibit a transition from the amorphous phase to the microcrystalline phase with increasing temperature. The film deposited at lower substrate temperature has the amorphous-like electronic structure with two types of dominant defect states corresponding to the occupied Si dangling bond states (D⁰/D^- and the empty Si dangling states (D⁺). At higher substrate temperature, the crystallinity of the deposited films increases, while their band gap energy decreases. Meanwhile, two types of additional defect states is incorporate into the films as compared with the amorphous counterpart, which is attributed to the interface defect states between the microcrystalline Si grains and the amorphous matrix. The relative SPS intensity of these two kinds of defect states in samples deposited above 300\du increases first and decreases afterwards, which may be interpreted as a result of the competition between hydrogen release and crystalline grain size increment with increasing substrate temperature.     

Dielectric properties of anodic films on sputter-deposited Ti-Si porous columnar films

For electrolytic capacitor application of the single-phase Ti alloys containing supersaturated silicon, which form anodic oxide films with superior dielectric properties, porous Ti-7 at% Si columnar films, as well as Ti columnar films, have been prepared by oblique angle magnetron sputtering on to aluminum substrate with a concave cell structure to enhance the surface area and hence capacitance. The deposited films of both Ti and Ti-7 at% Si have isolated columnar morphology with each column revealing nanogranular texture. The distances between columns are ∼500 nm, corresponding to the cell size of the textured substrate and the gaps between columns are 100-200 nm. When the porous Ti-7 at% Si film is anodized at a constant current density in ammonium pentaborate electrolyte, the growth of a uniform amorphous oxide film continues to ∼35 V, while it is limited to less than 6 V on the porous Ti film. The maximum voltage of the growth of uniform amorphous oxide films on the Ti-7 at% Si films is similar for both the flat and porous columnar films, suggesting little influence of surface roughness on the amorphous-to-crystalline transition of growing anodic oxide under the high electric field. Due to the suppression of crystallization to sufficiently high voltages, the anodic oxide films formed on the porous Ti-7 at% Si film shows markedly improved dielectric properties, in comparison with those on the porous Ti film.     

Effects of deposition temperature and thickness on the structural properties of thermal evaporated bismuth thin films

Bismuth (Bi) thin films of different thicknesses were deposited onto Si(1 0 0) substrate at various substrate temperatures by thermal evaporation technique. Influences of thickness and deposition temperature on the film morphologies, microstructure, and topographies were investigated. A columnar growth of hexahedron-like grains with bimodal particle size distribution was observed at high deposition temperature. The columnar growth and the presence of large grains induce the Bi films to have large surface roughness as evidenced by atomic force microscopy (AFM). The dependence of the crystalline orientation on the substrate temperature was analyzed by X-ray diffraction (XRD), which shows that the Bi films have completely randomly oriented polycrystalline structure with a rhombohedral phase at high deposition temperature (200 °C) and were strongly textured with preferred orientation at low deposition temperatures (30 and 100 °C).