Nano-cube MgO formed on silicon substrate using pulsed laser deposition

Nano-cube MgO particles were formed on Si substrates by deposition of an MgO target using pulsed laser deposition method. An epitaxial film grows on Si(001) substrate with its contraction of lattice constants. In this study, expecting high quality MgO film, the MgO film prepared in the oxygen pressure ranging from 75-400 mTorr at the high temperature of -750 degrees C. The deposited MgO showed the growth of (001) preferred orientation on the Si(001) substrate. However, X-ray Photoelectron Spectroscopy (XPS) indicated the MgO film did not form a continuous film on the Si surface. Interestingly, the surface morphology observed by an Atomic Force Microscopy (AFM) showed nano-cube MgO particles scattered on the smooth surface of Si substrate. After annealing the nano-cube MgO, the shape of MgO particles were changed from nano-cube to round shaped particles. The AFM image of the surface showed round shaped MgO nanoparticles scattered on rough surface. X-ray Diffraction (XRD) revealed the epitaxial growth of MgO(001) with cubic on cubic arrangement on the Si(001) substrate (MgO[100] parallel to Si[100]).     

Modified thermoelectric figure of merit estimated from enhanced mobility of [100] oriented beta-FeSi<Subscript>2</Subscript> thin film

The modification of thermoelectric figure of merit was estimated from enhanced mobility of [100] oriented beta-FeSi₂ film. beta-FeSi₂ on Si(001) substrate was prepared by molecular beam epitaxy method using an Fe source. The crystallographic orientation of beta-FeSi₂ film on Si(001) substrate was characterized by using X-ray diffraction. Using scanning electron microscopy, surface morphology and film thickness of samples were observed and estimated, respectively. The mobility of beta-FeS₂ film on Si(001) substrate were also characterized by Hall measurement at room temperature. A part of the enhancement of figure of merit was evaluated as the functions of mobility and crystallographic orientation of samples.     

Reflection high energy electron diffraction and X-ray studies of AlN films grown on Si(111) and Si(001) by organometallic chemical vapour deposition

The crystallinity of AlN films on silicon substrates grown by organometallic chemical vapour deposition was investigated using X-ray diffraction and reflection high energy electron diffraction (RHEED). Single-crystal films of good quality with atomically smooth surfaces can be epitaxially grown on Si(111) substrates. Epitaxial films can also be grown on Si(001) substrates. These films have previously been reported to have a fibre structure. Different RHEED patterns were observed from the films on Si(111) and Si(001). It is established that the films grown on Si(001) consist of two types of crystallite with the following orientations: [11$\text{2}$0]_AlN//[110]_Si and [11$\text{2}$0]_AlN//[1$\text{1}$0]_Si The thickness dependence of the crystallinity was also investigated. The standard deviation σ of the X-ray rocking curve for the films grown on Si(111) is less than that for the films on Si(001) and is independent of the film thickness. The σ values for the films on Si(001) decrease markedly with increasing film thickness. On the basis of these observations, the growth mechanism of AlN epitaxial films on Si(111) and Si(001) is discussed.     

Epitaxial growth and electrical measurement of single crystalline Pb(Zr0.52Ti0.48)O3 thin film on Si(001) for micro-electromechanical systems

We report in this work the epitaxial growth and the electrical characteristics of single crystalline Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin film on SrTiO₃(STO)-buffered Si(001) substrate. The STO buffer layer deposited by molecular beam epitaxy allows a coherent oxide/Si interface leading enhanced PZT crystalline quality. 70 nm-thick PZT (52:48) layer was then grown on STO/Si(001) by sol-gel method. X-ray diffraction demonstrates the single crystalline PZT film on Si substrate in the following epitaxial relationship: [110] PZT (001)//[110] STO (001)//[100] Si (001). The macroscopic electrical measurements show a hysteresis loop with memory window of 2.5 V at ± 7 V sweeping range and current density less than 1 μA/cm² at 750 kV/cm. The artificial domains created by piezoresponse force microscopy with high contrast and non-volatile properties provide further evidence for the excellent piezoelectric properties of the single crystalline PZT thin film.     

CVD金刚石薄膜(111)与(100)取向生长的热力学分析

用非平衡热力学耦合模型计算了CVD金刚石薄膜生长过程中C2H2与CH3浓度之比[C2H2]/[CH3]随衬底温度和CH4浓度的变化关系,从理论上探讨了金刚石薄膜（111）面和（100）面取向生长与淀积条件的关系。在衬底温度和CH4浓度由低到高的变化过程中,[C2H2]/[CH3]逐渐升高,导致金刚石薄膜的形貌从（111）晶面转为（100）晶面。添加氧后C2H2与CH3浓度都将下降,但C2H2下降得更多,因而添加氧也使[C2H2]/[CH3]下降,从而有利于生长（111）晶面的金刚石薄膜。     

Preparation of textured Mg2TiO4 thin filmson Si substrate by atmospheric pressure metallorganic chemical vapour deposition

Highly crystalline and fully [1 0 0]-textured Mg₂TiO₄ thin films have been successfully prepared on Si(1 0 0) and (1 1 1) substrate by using atmospheric pressure metallorganic chemical vapour deposition. Magnesium acetylacetonate was used as the metallorganic source. The films were produced in a horizontal warm-wall reactor. X-ray diffraction experiments provided evidence that the Mg₂TiO₄ thin films on Si substrate were fully textured with [1 0 0] orientation perpendicular to the substrate surface. The films obtained a very smooth and densely packed surface morphology. The relationship between substrate temperature and crystallographic orientations was also considered. This revised version was published online in July 2006 with corrections to the Cover Date.     

[001]织构和非织构CVD金刚石膜的电学特性

研究了「００１」织构和非织构金刚石膜的暗电流－电压特性、电流－温度特性以及在稳定Ｘ射线辐照下的响应。结果表明「００１」织构的金刚石膜相对非织构多晶金刚石膜具有大的暗电流和Ｘ射线响应。主要由于非织构金刚石膜含有大量的晶粒间界,导致对载流子的传输产生强烈散射。在高于５００Ｋ的温度区域内,随着温度的上升「００１」织构和非强构的金刚石膜的电流都将以指数式上升,这与Ｓｉ占据金刚石格点产生１．６８ｅＶ的激活能有关。     

Diamond thin film nucleation on silicon by ultrasonication in various mixtures

Nucleation is a very important step in synthetic diamond thin film growth process and generally the incubation time for the stable diamond nuclei formation is very long. We can consider it to be a pre-treatment of the Si substrate surface before diamond film deposition.In this study we have investigated the synthetic diamond thin film nucleation mainly on Si substrates by the ultrasonication in different mixtures of isopropanol, deionized water, n-methylpyrrolidon (NMP) or sodiumdodecylsulphate (SDS) containing nanosized diamond powder (≤10 nm, Sigma-Aldrich) and micro-or nanosized metals (Nickel, Cobalt, Yttrium). Liquids NMP and SDS have a special property to separate nanoparticles.     

Integration of BiFeO3 thin films on Si wafer via a simple sol-gel method

Integration of BiFeO₃ (BFO) films on Si substrate is desirable from an application point of view. The growth of (110)-textured BFO thin films with high quality on Si(100) substrate was realized by a seeding technique via a simple sol-gel method. Obviously switchable ferroelectric domains were observed, and in the meantime, the BFO films also exhibited a weak magnetization which somewhat showed dependence on the film thickness. Such an integration of the BFO films on Si constructed a metal/ferroelectric/insulator/semiconductor structure, which presented a memory feature as evidenced by capacitance-voltage hysteresis.     

The growth and transformation of Pd2Si on (111), (110) and (100) Si

Thin Pd films on (111), (110), (100) and amorphous Si substrates form [001] fiber textured Pd₂Si in the temperature range 100°–700°C. The degree of texture is a function of substrate orientation, increasing in the order amorphous Si, (100) Si, (110) Si and (111) Si. Only on the (111) Si substrate is the Pd₂Si film epitaxially oriented. Temperature-dependent growth on this orientation can be characterized by [001] textured growth, epitaxial azimuth orientation at the Si interface and progressive layer by layer formation of the mosaic crystal to the thin film surface.During Pd deposition, rapid non-diffusion-controlled growth of epitaxial Pd₂Si on (111) Si occurs at substrate temperatures of 100° and 200°C. An unidentified palladium silicide of low crystallographic symmetry forms during Pd deposition onto a 50°C substrate. The diffusion-controlled growth of Pd₂Si on (111) Si follows a t^0.5 dependence. The velocity constant is

$\text{k = 7 × 10}{}^{\mathrm{?2}}\text{exp}\text{?}\text{29200±800}\text{RT}\text{cm}{}^2\text{/}\text{sec}$

Palladium deposited on 100°C (111) Ge substrates reacts during deposition to form epitaxially oriented Pd₂Ge. However, growth of this phase at higher temperatures results in a randomly oriented film. The transformation of Pd₂Ge to PdGe is kinetically controlled. After a 15 min anneal at 560°±10°C in N₂ only PdGe is detectable on (111) Ge.The high temperature stability of thin film Pd₂Si is controlled by time- temperature kinetics. For a given annealing cycle, the nucleation and growth rates of the PdSi phase are inversely related to the crystalline perfection of Pd₂Si. Decreasing transformation rates follow the order (100), (110), (111) Si. formation of thin film Pd₂Si occurs by the formation of PdSi and subsequent growth of Si within the PdSi phase. After a 30 min N₂ anneal, initial transformation occurs at 735°C on (100) Si, 760°C on (110) Si and 840°C on (111) Si. Extended high temperature annealing produces a two-phase structure of highly twinned and misoriented Si and small PdSi grains that penetrate as much as 3 μm into the Si.     

Investigation of the nucleation mechanism in bias-enhanced diamond deposition on silicon and molybdenum

Polycrystalline diamond films were deposited on Si and Mo substrates in a microwave plasma-enhanced chemical vapour deposition reactor employing bias-enhanced nucleation. The deposition process was subdivided into two consecutive steps: the pretreatment (bias-enhanced nucleation) and the diamond growth step. To investigate the nucleation process we kept the deposition parameters during the diamond growth step constant and only changed the parameters during the pretreatment. The methods employed to analyze the deposited films after the pretreatment step were electron energy loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy.

The nucleation density (N_D) on Si following the complete deposition cycle (pretreatment and diamond growth step) increases considerably from 5 × 10⁸ cm⁻² to 5 × 10¹⁰ cm⁻² with an increase in the substrate temperature during the pretreatment (T_p) in the temperature range from 680 to 750 °C. For T_p ≥ 770 °C continuous films are formed. The structure of the pretreatment deposit undergoes likewise considerable changes: if T_p exceeds 770 °C the appearance of an intense diamond plasmon at 34 eV is observed, indicative of an increase in the concentration of diamond crystallites embedded in an otherwise amorphous carbon matrix. Our experiments suggest that diamond crystallites formed during the pretreatment serve as nucleation centres for the subsequent diamond growth.

The same deposition parameters which result in the formation of a continuous diamond film on Si, yield only low nucleation densities on Mo. An increase in N_D from 6 × 10⁶ cm⁻² to 2 × 10⁸ cm⁻² can be achieved by raising the methane concentration [CH₄] in the gas phase during the pretreatment from 5 to 50% (T_p = 820 °C). The carbon concentration at the surface for the pretreatment deposit, determined by XPS analysis, increases likewise with [CH₄]. According to the EELS analysis the structure of the pretreatment deposit is comparable with disordered graphite or a-C and no diamond plasmon is observed. The high [CH₄] is required to form the Mo-carbide interface and balance the diffusion of carbon into the metal before the a-C layer can be formed.

The formation of nucleation centres during the bias-enhanced nucleation seems under these deposition conditions to proceed via different pathways on Si and Mo. While the nucleation on Si appears to be linked to the formation of diamond nanocrystals during the pretreatment, this is not the case for Mo.     

Effect of reaction pressure on the nucleation behaviour of diamond synthesized by hot-filament chemical vapour deposition

Synthetic diamond particles were deposited on a Si (1 0 0) substrate using a hot-filament chemical-vapour-deposition method in order to study the effect of the reaction pressure on the nucleation behaviour. The reaction pressure was controlled, as an experimental variable, from 2 to 50 torr under the following conditions: a filament temperature of 2200 °C, a substrate temperature of 850 °C, a total flow rate of 200 s.c.c.m. and a methane concentration of 0.8 vol%. Diamond deposits on the Si wafer were characterized by micro-Raman spectroscopy, scanning electron microscopy (SEM) and optical microscopy.The maximum nucleation density of diamond particles on the unscratched Si substrate is shown at the reaction pressure of 5 torr. These phenomena can be explained by the competition effect between -SiC formation, which increases the diamond nucleation density, and atomic-hydrogen etching which decreases the nucleation sites.A new fabrication method for a high-quality diamond film without any surface pretreatments is introduced using a combination process between diamond nucleation at low pressure (5 torr) and growth at high pressure (30 torr).     

Lateral self-aligned p-type In2O3 nanowire arrays epitaxially grown on Si substrates

Lateral orientated growth of In2O3 nanowire (NW) and nanorod (NR) arrays has been achieved by a vapor transport and condensation method on (001) and (111) surfaces of Si substrates. The single crystalline In2O3 NWs and NRs were grown along [211] in parallel to the Si +/-[110] and lying in the substrate plane. The electrical measurements show that the In2O3 NWs are p-type semiconductor. By N+ doping, the resistivity of the In2O3 NWs has been tuned. The lateral self-aligned In2O3 NW and NR arrays on Si can offer some unique advantages for fabricating parallel nanodevices that can be integrated directly with silicon technology.     

Competitive Nucleation and Rapid Growth of Co-Si Intermetallic Compounds during Eutectic Solidification under Containerless Processing Condition

The liquid-solid transitions of (Co2Si+CoSi) and (CoSi+CoSi2) eutectic alloys were realized in drop tube and the rapid eutectic growth mechanism of intermetallic compounds was examined. The experimental and calculated results indicate that with increasing Co content, the intermetallic compound prefers nucleating primarily. The eutectic microstructures experience the transitions of ’lamellar-anomalous-divorced’ eutectic with undercooling. In undercooled state, the growth of CoSi intermetallic compound always lags behind others, and no matter how large the undercooling is, this intermetallic compound grows under the solutal diflusion control. The calculated coupled zone demonstrates that (Co2Si+CoSi) eutectic can form within certain undercooling regime, when the composition is in the range from 23.6% to 25.4% Si. And the calculated coupled zone of (CoSi+CoSi2) covers a composition range from 40.8% to 43.8% Si.     

Self-organization of cobalt-silicide nanoislands on stepped Si(111) as a function of growth method

When silicides, such as CoSi2, are grown in the form of nanoislands they frequently exhibit nanometer size effects, which can be useful for single electron devices. For such devices, however, lateral self-organization is required. In this work, step-aided self-organization of CoSi2 nano-islands is demonstrated on a vicinal (stepped) Si(111) substrate. Straight and equidistant steps or step-bunches are routinely obtained on the vicinal Si(111), creating almost ideal template for self-organization. Two growth methods were examined: solid-phase epitaxy (SPE), where Co was deposited at room temperature and annealed to promote silicide formation, and reactive deposition epitaxy (RDE) where Co was deposited at elevated temperature. While the latter did not result in any noticeable ordering, due to instantaneous reaction with Si in course of deposition, the former lead to preferential occupation of step-bunch sites by the silicide nanoislands. Furthermore, self-limiting growth caused narrow distribution of island sizes and island-island separation distances.     

Growth Kinetics and Microstructure of PbTe Films Produced on Si and BaF<Subscript>2</Subscript> Substrates by a Modified Hot-Wall Method

Lead telluride films have been grown on Si (100) and BaF₂ (100) substrates by a modified hot-wall method using a graphite reaction chamber. According to X-ray diffraction, X-ray microanalysis, and scanning electron microscopy characterization results, the average growth rate of PbTe films having compositions within the homogeneity range of lead telluride increases with increasing lead vapor partial pressure and decreases with increasing tellurium vapor partial pressure, independent of the nature of the substrate. The rate of PbTe film growth has been shown to be maximal in the initial stage of the process and decrease monotonically over time, independent of the nature of the substrate. Independent of the growth time, the average growth rate of the PbTe films on the Si (100) substrates is considerably higher than that on the BaF₂ (100) substrates. Reflection high-energy electron diffraction data indicate that the texture of the PbTe films on Si (100) corresponds to the substrate orientation and that the misorientation angle of the mosaic blocks does not exceed 20°. On the BaF₂ (100) substrates, we observe epitaxial PbTe film growth with the orientation relationship (100), [011] PbTe ║ (100), [011] BaF₂.     

不同衬底上低温生长的ZnO晶体薄膜的结构及光学性质比较

采用电子束反应蒸发方法,在单晶Si(001)及玻璃衬底上低温外延生长了沿c轴高度取向的单晶ZnO薄膜,并对沉积的ZnO晶体薄膜的结构和光学性质进行了分析比较。通过对ZnO薄膜的X射线衍射(XRD)分析及光致荧光激发谱(PLE)测量,研究了衬底材料结构特性、生长温度及反应气氛中充O     

衬底表面预处理对金刚石薄膜形核及长大的影响

用燃烧火焰法在 TC4 Ti 合金和单晶 Si(001)面上沉积了金刚石薄膜。对合成的膜进行了扫描电镜、激光喇曼光谱分析。结果表明,金刚石薄膜的结构和形貌强烈取决于沉积温度、O_2/C_2H_2流量比等工艺参数。研究了衬底表面预处理对金刚石薄膜形核及长大的影响,并对表面预处理影响形核的原因进行了初步探讨。     

Growth of SrTiO3 thin epitaxial films by aerosol MOCVD

SrTiO₃ thin films were prepared by aerosol metal-organic chemical vapour deposition on (001) MgO, R-plane Al₂O₃ and (001) Si single-crystal substrates. Strontium tetramethyl heptadionate and titanium n-butoxide dissolved in diethyleneglycol dimethyl ether were used as precursors. The structure of the films was investigated by X-ray diffraction and transmission electron microscopy. Epitaxial films with [001] and [111] orientation perpendicular to the substrate surface were obtained on MgO and Al₂O₃, respectively. The epitaxial films on the MgO substrate were found to be in a relaxed state with lattice parameters corresponding to the bulk values. SrTiO₃ films on the Si substrate were grown as highly textured in the [011]direction and randomly oriented in the plane parrallel to the substrate surface.     

氢和硼离子轰击可消除(001)面多晶金刚石膜的空位缺陷

在微波等离子体化学气相沉积金刚石膜时,采用负偏压使氢和硼离子轰击金刚石膜表面。发现单纯的氢离子的轰击会导致表面刻蚀,可使（001）面颗粒尺寸增大,用扫描电镜（SEM）和阴极发射光谱（CL）分析了硼离子掺杂后[001]取向的金刚石膜表面,发现CL中A峰消失,表明薄膜中位错密度降低,首次发现CL谱中741.5nm峰和575nm到625nm宽峰明显下降,表明在金刚石膜中,中性空位和氮空位缺陷基本消失,利用小原子穿透理论解释了这个现象。