Au/Au(100)外延薄膜生长的计算机模拟及其微观机制研究

在分子动力学研究的基础上建立了气相沉积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MonteCarlo方法研究了Au/Au(100)外延薄膜的初期生长过程,探讨了薄膜外延生长随基体温度的变化.通过气相外延沉积的计算机模拟发现:单原子扩散过程在薄膜生长中起着极为关键的作用.当薄膜生长温度低于单原子的扩散温度时,表面原子的成核和表面岛的生长主要是由沉积原子的空间随机性和表面原子密度增加而决定的;随着薄膜生长温度的提高。

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MonteCarlo方法研究了载能粒子沉积Au/Au(10 0 )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(10 0 )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 .载能粒子是通过改变薄膜局域表面形貌而影响着薄膜的生长行为 。

不同温度及外加磁场方向外延生长Ni-Mn-Ga薄膜的磁性能研究

外延生长Ni–Mn-Ga哈斯勒合金薄膜具有多种优异的磁控功能行为,是智能传感驱动、新型固态制冷等领域中极具前景的候选材料.利用磁控溅射在MgO(001)单晶基板上制备出外延生长Ni-Mn-Ga薄膜,X射线衍射和微观组织表征结果显示其在室温下为七层调制结构马氏体.通过测量MgO(001)基板上外延生长Ni-Mn-Ga薄膜在不同温度和不同磁场方向的磁滞回线发现,当温度低于330K时,在其磁滞回线上能够观察到明显的"磁矩跳跃"现象(磁化强度的突变),并且随温度降低该现象越明显;当温度高于335 K时,薄膜的磁滞回线为常规磁性材料的磁滞回线,说明"磁矩跳跃"现象只存在于马氏体状态.通过研究不同施加磁场方向的磁滞回线发现,薄膜磁滞回线上的"磁矩跳跃"现象对外加磁场方向也非常敏感,只有当外加磁场靠近MgO单晶基板的[100]或[010]方向时,薄膜的磁滞回线才会存在明显的"磁矩跳跃"现象.

薄膜外延生长及其岛核形成的计算机模拟

以Cu膜为例, 用Monte Carlo算法模拟了薄膜生长的随机过程. 找到了生长过程中的三个优化温度, 并研究了它们的渐近一致性, 同时对各种温度区间内表面粗糙度、相对密度随入射率的变化规律进行深入的探讨. 模拟中考虑了一些新的效应, 如原子迁移过程中势能的变化, 以及原子扩散引起的连带效应, 从而使模拟更加合理. 模型中采用了冻结周围原子近似和周期性边界条件处理.

Growth of Thin Silicon on Sapphire (SOS) Film Materials and Device Applications

The increasing emphasis on the sub\|micron CMOS/SOS devices has placed a demand for high quality thin silicon on sapphire (SOS) films with thickness of the order 100-200nm. It is demonstrated that the crystalline quality of as\|grown thin SOS films by chemically vapor deposition method can be greatly improved by solid phase epitaxy (SPE) process: implantation of self\|silicon ions and subsequent thermal annealing. Subsequent regrowth of this amorphous layer leads to a great improvement in silicon layer crystallinity and channel carrier mobility, respectively by double crystal X\|ray diffraction and electrical measurements. Thin SPE SOS films would have application to the high\|performance CMOS circuitry.

Plasma Treatment Enhanced Magnetic Properties in Manganese Doped Titanium Nitride Thin Films

The ferromagnetic manganese doped TiN films were grown by plasma assisted molecular beam epitaxy on MgO（001） substrates. The nitrogen concentration and the ratio of manganese at Ti lattice sites increase after the plasma annealing post treatment. TIN（002） peak shifts toward low angle direction and TiN（111） peak disappears after the post treatment. The lattice expansion and peak shift are mainly ascribed to the reduction of nitrogen vacancies in films. The magnetism was suppressed in as-prepared sample due to the pinning effect of the nitrogen vacancies at defect sites or interface. The magnetism can be activated by the plasma implantation along with nitrogen vacancies reduce. The decrease of nitrogen vacancies leads to the enhancement of ferromagnetism.

Epitaxial α″-Fe_(16)N_2 Films Grown on NaCl (001) by Facing Target Sputtering

There is a gr eat interest in obtaining epitaxial α″ nitride phase of iron because of their special ferromagnetic properties. α″ Fe 16 N 2 thin films have been prep ared by facing target sputtering (FTS) onto NaCl (001) substrates in a mixture of argon(Ar) and N 2 gases. The base pressure was 6×10 -5 Pa. During sput tering, the partial pressures of Ar and N 2 gases were kept constant at 0.3 Pa and 0.05 Pa respectively. The deposition rate was about 0.2 nm/s. The substrate temperature was held at about 100 ℃. Annealing of the films was sequentially ca rried out at 150 ℃ for 1 h in vacuum ( at least 10 -4 Pa ) to obtain α″ phase. Transmission electron microscope (TEM) observations and X ray diffract ion (XRD) patterns showed that the α″ Fe 16 N 2 epitaxially grew on the NaCl substrates. It was found that the arrangement of the SAD patterns exhibits perfect symmetries.By using super lattice reflections, the lattice constants a=b=(5.71±0.02)×10 -1 nm and c=(6.30±0.04) ×10 -1 nm of the α″ phase with a body centered tetragonal (BCT) structu re were determined, which was very close to the results obtained by Jack (a=b= 5.72×10 -1 nm, c= 6.29×10 -1 nm). The X ray diffraction patterns and the selected area diffraction patterns showed t hat α″ Fe 16 N 2 epitaxially grew on the NaCl (001) substrate with orien tation relationships α″ Fe 16 N 2 (001) ‖NaCl (001),α″ Fe 16 N 2 ‖NaCl .

Uniformity of Electrical Parameters on MCT Epitaxy Film

For Hall measurement under different magnetic fields at LN2 temperature,Hg1-xCdxTe （MCT） film （radius 1 cm） grown on CdTe substrate by LPE is photoengraved into many small Van Der Pauw squares,then their Hall coefficients and mobilities are measured and analyzed,respectively.Two films were Hall-tested during the temperature range from LHe 4.2 K to about 200 K.An actual impression on the uniformity of electrical parameters for MCT film can obtained by means of the methods presented in this paper.

反应限制聚集模型的动力学行为的研究

根据反应限制聚集(reactionlimitedaggregation,RLA)模型,研究表面活性剂存在时的薄膜外延生长动力学过程.研究结果表明,在二维岛的生长初期,分形岛与紧致岛具有不同的岛密度和“死”原子密度(岛的相对总面积)增长方式:分形岛密度随覆盖率生长指数小于1,紧致岛密度的生长指数大于1;分形岛相对总面积随覆盖率线性增长,紧致岛相对总面积随覆盖率非线性增长.

Design and fabrication of superconducting HEB mixer

This paper describes the design and fabrication of superconducting hot electron bolometer (HEB) mixer based on ultra-thin superconducting NbN films. The high quality films were epitaxially grown on high resistance Si substrates. The device was fabricated by magnetron sputtering, electron beam lithography (EBL), reactive ion etching (RIE), lithography, and so on. The device's resistance-tempera-ture (R-T) curves and current-voltage (I-V) curves were studied. The results of THz response of the device are presented. Y-factor technique was used to measure the device's noise temperature. When the device was irradiated with a laser radiation of 2.5 THz, the obtained lowest noise temperature of the device was 2213 K.

4H-SiC trench gate MOSFETs with field plate termination

Field plate(FP)-terminated 4H-SiC trench gate MOSFETs are demonstrated in this work.N+/P?/N?/N+multiple epitaxial layers were grown on 3-inch N+type 4H-SiC substrate by chemical vapor deposition(CVD),and then the 4H-SiC trench gate MOSFETs were fabricated based on the standard trench transistor fabrication.Current-voltage measurements in forward and reverse bias have been performed on different devices with and without FP protections.It is found that more than 60%of the devices protected with FP termination are able to block 850 V.The measurements also show that the devices have the small leakage currents 0.15 nA at 600 V and 2.5 nA at 800 V,respectively.The experimental results also were compared with the simulated results,which show good agreement with each other in the trend.The limited performance of the devices is mainly because of the damage induced on the trench sidewalls from the etching process and the quality of the SiO2 films.Therefore,the 4H-SiC trench gate MOSFETs are expected to be optimized by reducing the etching damage and growing high-quality SiO2 dielectric films.

Epitaxial growth of ultrathin ZrO_2(111) films on Pt(111)

Ordered epitaxial ZrO2 films were grown on Pt(111) and characterized by low energy electron diffraction (LEED), synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS). The films were prepared by vapor deposition of zirconium in an O2 atmosphere followed by annealing under ultra high vacuum. At low coverages, the films grew as discontinuous two-dimentional islands with ordered structures. The size and structure of these islands were dependent on the coverage of ZrO2 films. At coverage <0.5 monolayer (ML), ( 19^(1/2) × 19^(1/2)) R23.4° and (5×5) structures coexisted on the surface. As the coverage increased, the (19^(1/2) × 19^(1/2) ) R23.4° structure developed with increasing degree of long-range order, while the (5×5) structure gradually faded. When the coverage reached >6 ML, a continuous ZrO2(111) film was formed with a (1×1) surface LEED pattern coexisting with a (2×2) pattern. These ordered thin ZrO2 films provide good model surfaces of bulk ZrO2 and can be used for further fundamental studies of the surface chemistry of ZrO2 using modern surface science techniques.

GaN PIN betavoltaic nuclear batteries

GaN PIN betavoltaic nuclear batteries are demonstrated in this work. GaN epitaxial layers were grown on 2-inch sapphire sub-strates by MOCVD, and then the GaN PIN nuclear batteries were fabricated. Current-voltage （l-V） characteristic shows that the small leakage currents are 0.12 nA at 0 V and 1.76 nA at -10 V, respectively. With 147Pm the irradiation source, the maximum open circuit voltage and maximum short circuit current are 1.07 V and 0.554 nA, respectively. The fill factor （FF） of 24.7% for the battery was been obtained. The limited performance of the devices is mainly due to the low energy deposition in the microbatteries. Therefore, the GaN nuclear microbatteries are expected to be optimized by growing high quality GaN films, thin dead layer and so on.

Epitaxial growth and in-plane dielectric properties of orthorhombic HoMnO_3 films

Orthorhombic HoMnO3(HMO) thin films were grown epitaxially on LaAlO3(001) substrates by using pulsed laser deposition technique. The films showed perfect orthorhombic crystallization and were well-aligned with the substrates. The in-plane dielectric constant and loss of HMO films were measured as functions of temperature(80–300 K) and frequency(120 Hz–100 kHz) by using coplanar interdigital electrodes. Two thermally activated dielectric relaxations were found, and the respective peaks shifted to higher temperatures as the measuring frequency increased. The in-plane dielectric properties of epitaxial orthorhombic HMO films were considered as universal dielectric response behavior, and the dipolar effects and the hopping conductivity induced by the charge carriers were used to explain the results.

Room-temperature epitaxial growth of V_2O_3 films

Herein we report the room-temperature epitaxial growth of V203 films by laser molecule beam epitaxy. X-ray diffraction pro- files show the room-temperature epitaxial V2O3 films orient in the [ 110] direction on α-Al2O3 （0001） substrates. Atomic force microscopy measurements reveal that the ultra-smooth surfaces with root-mean-square surface roughness of 0.11 nm and 0.28 nm for 10-nm-thick and 35-nm-thick V2O3 film, respectively. X-ray photoelectron spectroscopy results indicate the V3＋ oxida- tion state in the films. Typical metal-insulator transition is observed in films at about 135 K. The resistivities at 300 K are ap- proximately 0.8 mΩ cm and 0.5 mΩ cm for 10-rim-thick and 35-nm-thick V203 film, respectively.