Semi-insulating GaAs grown in outer space

A semi-insulating GaAs single crystal ingot was grown in a recoverable satellite, within a specially designed pyrolytic boron nitride crucible, in a power-traveling furnace under microgravity. The characteristics of a compound semiconductor single crystal depends fundamentally on its stoichiometry, i.e. the ration of two types of atoms in the crystal. a practical technique for nondestructive and quantitative measuring stoichiometry in GaAs single crystal was used to analyze the space-grown GaAs single crystal. The distribution of stoichiometry in a GaAs wafer was measured for the first time. The electrical, optical and structural properties of the space-grown GaAs crystal were studied systematically, Device fabricating experiments prove that the quality of field effect transistors fabricated from direct ion-implantation in semi-insulating GaAs wafers has a close correlation with the crystal's stoichiometry. (C) 2000 Elsevier Science S.A. All rights reserved.

Boron diffusion in Ge+ premorphized and BF2+ implanted Si(001)

The annealing behavior of Si implanted with Ge and then BF2 has been characterized by double crystal X-ray diffraction (DCXRD) and secondary ion mass spectroscopy (SIMS). The results show that annealing at 600 degrees C for 60 minutes can only remove a little damage induced by implantation and nearly no redistribution of Ge and B atoms has occurred during the annealing. The initial crystallinity of Si is fully recovered after annealing at 950 degrees C for 60 minutes and accompanied by Ge diffusion. Very shallow boron junction depth has been formed. When annealing temperature rises to 1050 degrees C, B diffusion enhances, which leads to a deep diffusion and good distribution of B atoms into the Si substrate. The X-ray diffraction (004) rocking curves from the samples annealed at 1050 degrees C for 60 minutes display two SiGe peaks, which may be related to the B concentration profiles.

离子注入选育维生素C高产菌

维生素C二步发酵混菌生产中，第一步由单菌发酵将D-山梨醇转化为L-山梨糖，第二步由产酸菌氧化葡萄糖酸杆菌与伴生菌巨大牙孢杆菌混菌发酵将L-山梨糖转化为2-酮基-L-古龙酸（维生素C的前体物）.利用离子注入技术，采用N<'+>离子束为诱变源，诱变维生素C二步混菌发酵中的产酸菌氧化葡萄糖酸杆菌.通过建立的维生素C高产菌筛选方法，以2-酮基-L古龙酸为筛选标记，获得一株维生素C高产菌株D14，其与生产用伴生菌巨大牙孢杆菌组成维生素C新混合菌系ND14，平均醇酸转化率比生产用混菌提高3.3个百分点.维生素C高产菌株D14及维生素C新混合菌系ND14生长特性及发酵特性为：维生素C高产菌株D14生长能力明显增强;维生素C新混合菌系D14于种子培养基中稳定期延长8-12小时，总生物量增加;在发酵过程中ND14生长明显快于CK，菌体总生物量增加.利用均匀设计的方法对新混合菌系ND14发酵培养基进行了优化，其结果为：最适玉米浆浓度为1.6%、最适尿素浓度为1.6%、最适MgSO<,4>浓度为0.03%、最适KH<,2>PO<,4>浓度为0.06%.

Influence of processing medium on frictional wear properties of ball bearing steel prepared by laser surface melting coupled with bionic principles

Coupling with bionic principles, an attempt to improve the wear resistance of ball bearing steel (GCr15) with biomimetic units on the surface was made using a pulsed Nd: YAG laser. Air and water film was employed as processing medium, respectively. The microstructures of biomimeitc units were examined by scanning electron microscope and X-ray diffraction was used to describe the microstructure and identify the phases as functions of different mediums as well as water film with different thicknesses. The results indicated that the microstructure zones in the biomimetic specimens processed with water film were more refined and had better wear resistance increased by 55.8% in comparison with that processed in air; a significant improvement in microhardness was achieved by laser surface melting. The application of water film provided considerable microstructural changes and much more regular grain shape in biomimetic units, which played a key role in improving the wear resistance of ball bearing steel. (c) 2010 Elsevier B.V. All rights reserved.

碳化硅中氦离子高温注入引出的缺陷及其退火行为的光谱研究

6H-SiC single crystal specimens were implanted at 600 K with 100 KeV He ions to three successively increasing fluences and subsequently annealed at different temperatures ranging from 600℃ to 1200℃ in vacuum.After the annealing,the samples were investigated by using Raman scattering spectroscopy and photoluminescence spectrometry,respectively.Both of the two methods showed that the damage induced by helium-ion-implantation in the lattice is closely related to the dose.The thermal annealing brings about reco...中文摘要：对氦(He)离子高温(600K)注入6H-SiC中的辐照缺陷,在阶梯温度退火后演化行为的拉曼光谱和室温光致发光谱的特征进行了分析.这两种方法的实验结果表明,离子注入所产生晶格损伤的程度与注入剂量有关;高温退火导致损伤的恢复,不同注入剂量造成的晶格损伤需要不同的退火温度才可恢复.在阶梯温度退火下呈现出了点缺陷的复合、氦-空位团的产生、氦泡的形核、长大等特性.研究表明:高温(600K)注入在一定剂量范围内是避免注入层非晶化的一个重要方法,为后续利用氦离子注入空腔掩埋层吸杂或者制备低成本、低缺陷密度的绝缘层上碳化硅(SiCOI)材料提供了可能.

碳化硅中氦离子高温注入引入的缺陷及其退火行为的光谱研究

对氦(He)离子高温(600K)注入6H-SiC中的辐照缺陷,在阶梯温度退火后演化行为的拉曼光谱和室温光致发光谱的特征进行了分析.这两种方法的实验结果表明,离子注入所产生晶格损伤的程度与注入剂量有关;高温退火导致损伤的恢复,不同注入剂量造成的晶格损伤需要不同的退火温度才可恢复.在阶梯温度退火下呈现出了点缺陷的复合、氦-空位团的产生、氦泡的形核、长大等特性.研究表明:高温(600K)注入在一定剂量范围内是避免注入层非晶化的一个重要方法,为后续利用氦离子注入空腔掩埋层吸杂或者制备低成本、低缺陷密度的绝缘层上碳化硅(SiCOI)材料提供了可能.

Annealing effects in silicon implanted with helium

Silicon samples were implanted with helium and analyzed by atomic force microscopy (AFM) and Raman spectroscopy before and after annealing in the range of 523-1273 K. After annealing at 523 K, the amorphous area induced by He-ion implantation at room temperature was partially recovered and grain sizes became larger. The surface morphology was analyzed through AFM measurements and it was observed that root mean square of the surface roughness alters upwards and then downwards with annealing temperature. (C) 2008 Elsevier B.V. All rights reserved.

Surface morphology of He-implanted single-crystalline silicon

Single-crystalline Si (100) samples were implanted with 30 keV He2+ ions to doses ranging from 2.0x10(16) to 2.0x10(17) ions/cm(2) and subsequently thermally annealed at 800 degrees C for 30min. The morphological change of the samples with the increase of implantation dose was investigated using atomic force microscopy (AFM). It was found that oblate-shaped blisters with an average height around 4.0nm were found on the 2.0 x 10(16) ions /cm(2) implanted sample surface; spherical-shaped blisters with an average height wound 10.0nm were found on the 5.0 x 10(16) ions/cm(2) implanted sample surface; strip-shaped and conical cracks were observed on the sample He-implanted to a dose of 1.0 X 10(17) ions /cm(2). Exfoliations occurred on the sample surface to a dose of 2.0 x10(17) ions /cm(2). Mechanisms underlying the surface change were discussed.

Structural and optical properties of 6H-SiC helium-implanted at 600 K

Single crystals of 6H-SiC were implanted at 600 K with 100 key He ions to three successively fluences and subsequently annealed at different temperatures ranging from 873 to 1473 K in vacuum. The recovery of lattice damage was investigated by different techniques including Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy and Fourier transform infrared spectroscopy. All three techniques showed that the damage induced by helium ion implantation in the lattice is closely related to the fluence. Rutherford backscattering spectrometry/channeling data on high temperature implantations suggest that for a fluence of 3 x 10(16) He+/cm(2), extended defects are created by thermal annealing to 1473 K. Apart from a well-known intensity decrease of scattering peaks in Raman spectroscopy it was found that the absorbance peak in Fourier transform infrared spectroscopy due to the stretching vibration of Si-C bond shifted to smaller wave numbers with increasing fluence, shifting back to larger wave numbers with increasing annealing temperature. These phenomena are attributed to different lattice damage behavior induced by the hot implantation process, in which simultaneous recovery was prevailing. (C) 2010 Elsevier B.V. All rights reserved.

Enhanced photoluminescence of Ar+ implanted sapphire before and after annealing

In this paper, we studied the changes in the photoluminescence spectra of the Ar+ ion implanted monocrystalline sapphire annealed at different atmospheres and different temperatures. Single crystals of sapphire (Al2O3) with the (1 0 (1) over bar 0) (m-samples) orientation were implanted at 623 K with 110 keV Ar+ ions to a fluence of 9.5 x 10(16) ions/cm(2). Photoluminescence measurement of the as-implanted sample shows a new emission band at 506 nm, which is attributed to the production of interstitial Al atoms. The intensity of emission band at 506 nm first increased then decreased with increase in annealing temperature. For the same annealing temperature, the intensity of PL peak at 506 nm of the sample annealed in air was higher than the sample annealed in vacuum. The experimental results show that the intensity of the PL peak at 506 nm of Ar-implanted sapphire can be enhanced by subsequent annealing with an enhancement of nearly 20 times. The influence of thermal annealing of the Ar-implanted samples on the new 506 nm emission band was discussed. (C) 2009 Elsevier B.V. All rights reserved.

利用惰性气体离子注入制备Au纳米颗粒/蓝宝石复合材料

在绝缘体衬底中金属纳米颗粒的制备，常采用金属离子直接注入的方法，这一方法存在的问题主要是，所形成的金属颗粒尺寸离散较大，使这类材料的应用受到了限制。惰性气体离子注入到某些材料中所形成的纳米气泡或空腔的尺寸分布较均一，且纳米空腔具有吸附金属离子的性质。在此基础上我们提出：利用惰性气体离子注入预先在材料中形成尺寸分散较小的纳米空腔埋层，然后在样品表面沉积Au膜，再尝试通过高温扩散或离子束附加辐照的方法制备Au纳米颗粒。实验结果表明，高温退火的方法未在样品内部形成Au颗粒，离子束附加辐照的方法在样品内形成了尺寸分散较小的Au纳米颗粒，这为制备尺寸分散小的金属纳米颗粒复合材料提供了借鉴和新方法。论文中用多种测试方法（PL、UV-VIS、RBS、SEM、TEM）分析讨论了Ar的注入剂量、热处理温度、样品表面取向等参量对制备Au纳米颗粒的影响，并利用M-G理论对所研究体系的光吸收性质进行了模拟计算和定性解释

Fabrication of GdSi2 film by low-energy ion-beam implantation

Single-phase gadolinium disilicide was fabricated by a low-energy ion-beam implantation technique. Auger electron spectroscopy and X-ray photoelectron spectroscopy were used to determine the composition and chemical states of the film. The structure of the sample was analyzed by X-ray diffraction and the surface morphology was investigated by scan electron microscopy. Based on the measurements, only orthorhombic GdSi2 phase was found in the sample and the surface morphology was pitting. After annealing at 350degreesC for 30 min at Ar atmosphere, the full-width at half-maximum of GdSi2 became narrower. It indicates that the GdSi2 is crystallized better after annealing. (C) 2003 Elsevier B.V. All rights reserved.