Comparative hall measurements on wet- and dry-oxidized 4H-SiC MOSFETs

Hall measurements have been used to compare the properties of 4H-SiC inversion-mode MOSFETs with “wet” and “dry” gate oxides. While the field-effect mobilities were approximately 3–5 cm²/Vs, the Hall mobilities in 4H-SiC MOSFETs in the wet and dry oxide samples were approximately 70–80 cm²/Vs. The dry-oxidized metal oxide semiconductor field effect transistors (MOSFETs) had a higher transconductance, improved threshold voltage, improved subthreshold slope, and a higher inversion carrier concentration compared to the wet-oxidized MOSFETs. The difference in characteristics between the wet- and the dry-oxidized MOSFETs is attributed to the larger fixed oxide charge in the dry oxide sample and a higher interface trap density in the wet oxide sample.     

长脉冲激光沉积原位生成YBaCuO超导膜

用长脉冲激光(脉冲宽度150μs,波长1.06μm)辐照高温烧结的YBa_2Cu_3O_(7-x)靶,在6Pa的氧气压强下,巳在(100)YSZ单晶衬底上原位生成YBa_2Cu_(?)O_(7-x)超导膜。衬底置于750℃的加热器上,衬底与靶之间的距离5cm,用该法制得的薄膜光亮坚实,正常态呈金属性,零电阻温度为84.7K。用XRD和SEM对薄膜进行了分析研究。     

脉冲激光沉积SrBi2Ta2O9铁电薄膜电容特性研究

用ＰＬＤ方法成功地制备了ＳＢＴ铁电薄膜，并制作成Ｐｔ／ＳＢＴ／Ｐｔ薄膜电容器。ＳＢＴ薄膜的晶面取向以（００８）和（１１５）为主。在５Ｖ电压下，极化反转，并且得到较饱和的电滞回线，剩余极化强度和矫顽电场分别为８４μＣ／ｃｍ２和５７ｋｖ／ｃｍ。ＩＶ特性测试显示两个对称的双稳峰，并得到零电压下，面积为３１４×１０４μｍ２，厚度为０３５μｍ的电容器，电容约为５６０ｐＦ，介电常数约为６００。疲劳测试表明Ｐｔ／ＳＢＴ／Ｐｔ具有优良的抗疲劳特性。     

新一代静止图像压缩标准JPEG2000

随着多媒体应用领域的扩展,传统的图像压缩技术已无法满足人们对多媒体图像的要求,各种图像压缩格式应运而生,如JPEG、MPEG-4VTC、PNG等。其中新一代ISO/ITU-T静止图像压缩标准JPEG2000成为热点。文章重点介绍JPEG2000图像编码系统的基本思想及其特性。     

叶绿素衍生物─CPD_4在人血清中的激发和发射荧光谱

叶绿素衍生物４号（ＣＰＤ４）是一种新型中药光敏剂，本文研究了不同浓度的ＣＰＤ４分别在含１０％不同血型人血清的生理盐水中以及纯生理盐水中的激发和发射荧光光谱，并对结果进行了分析，结论对ＣＰＤ４在光动力诊断恶性肿瘤的临床应用具有一定的指导意义．     

K0.9Li0.1（Ta0.5Nb0.5）O3晶体压电应变系数的测量

用准静态ｄ＿（３３）测量仪和干涉法相结合。测量了Ｋ＿（０．９）Ｌｉ＿（０．１）（Ｔａ＿（０．５）Ｎｂ＿（０．５）Ｎｂ＿（０．５））Ｏ＿３晶体的压电应变系数。结果为：ｄ＿（３３）＝８６．０，ｄ＿（３３）＝一２９．５，ｄ＿（１５）＝１１２．９×１０￣（－１２）Ｃ／Ｎ．     

ZrO_2（Y－TZP）－Si_3N_4复合材料中抑制ZrN生成研究

研究了气氛加压烧成ＺｒＯ２（Ｙ－ＴＺＰ）－Ｓｉ３Ｎ４复合材料中抑制ＺｒＮ生成工艺问题，相组成分析表明：无论添加２０ｗｔ％工业ＺｒＯ２或者Ｙ－ＴＺＰ（３ｍｏｌ％Ｙ。Ｏ。）的氯化硅复合材料，在低于１８５０℃，３ＭＰａｋ气压力下烧成，表面无ＺｒＮ生成．通过加入有效的烧结助剂（Ｙ。Ｏａ＋ＡＩ。Ｏｓ）、增加埋粉中ＳＩＯ分压以及增加保护气氛氮气压力，适当的烧成条件等工艺措施可有效地抑制ＺｒＮ的生成．实验还证实了ＺｒＮ很容易氧化，含有ＺｒＮ的ＺｒＯ。（Ｙ－ＴＺＰ）－ＳｉｓＮ。复合材料试样经９００℃，０．ｓｈ热处理已粉碎性裂开．     

汉白玉废料制备球形纳米碳酸钙的研究

将汉白玉废料通过高温煅烧分解得到氧化钙,再用氯化铵循环液溶解氧化钙制得碱性氯化钙溶液,除去其中的Mg、Fe等杂质得到氯化钙精制溶液,利用化学方法合成得到碳酸钙粉体.用X射线衍射(XRD)、扫描电镜(SEM)及激光粒度分析仪、白度仪对碳酸钙产品的晶相组成、形貌、粒度分布、白度及化学组成进行了分析,所得产品为纯度达98.5%以上、白度达97%以上、平均粒度为80nm左右的球形纳米级碳酸钙.并对碳化反应速率及合成球形纳米碳酸钙的影响因素进行了分析.实验中循环使用NH4Cl,氨的排放量小,减少了环境污染.     

Studies on the corrosion behavior of cerium-implanted zircaloy-4 with GAXRD

In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zircaloy-4, specimens were implanted by cerium ions with a fluence range from 1×10¹⁶ to 1×10¹⁷ ions/cm² at maximum 150°C, using MEVVA source at an extracted voltage of 40 kV. The valence and elements penetration distribution of the surface layer were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES) respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the cerium ion implantation in the oxide films. Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zircaloy-4 in a 1 N H₂SO₄ solution. It was found that a significant improvement in the aqueous corrosion behavior of zircaloy-4 implanted with cerium ions compared with that of the as-received zircaloy-4. The improvement effect will declined with raising the implantation fluence. The bigger is the fluence, the less is the improvement. Finally, the mechanism of the corrosion behavior of the cerium-implanted zircaloy-4 is discussed.