退火对B掺杂纳米金刚石薄膜微结构和电化学性能的影响

采用热丝化学气相沉积法制备B掺杂纳米金刚石薄膜,并对薄膜进行真空退火处理,系统研究了不同退火温度对B掺杂纳米金刚石薄膜的微结构和电化学性能的影响.结果表明,当退火温度升高到800 ℃后,薄膜的Raman谱图中由未退火时在1157,1346,1470,1555 cm^-1处的4个峰转变为只有D峰和G峰,说明晶界上的氢大量解吸附量减少,并且D峰和G峰的积分强度比I_D/I_G值变为最小,即sp²相团簇     

退火时间对硼掺杂纳米金刚石薄膜微结构和电化学性能的影响

采用高分辨透射电镜、紫外和可见光Raman光谱及循环伏安法研究了1000 ℃下退火不同时间的硼掺杂纳米金刚石薄膜的微结构和电化学性能. 结果表明,随退火时间的延长,薄膜中纳米金刚石晶粒尺寸逐渐减小.当退火时间为0.5 h时, 金刚石晶粒尺寸由未退火样品的约15 nm减小为约8 nm, 金刚石相含量增加;当退火时间为2.0 h时,金刚石晶粒减小为2—3 nm, 此时晶界增多,金刚石相含量减少;退火时间为2.5 h时纳米金刚石晶粒尺寸和金刚石相含量又略有上升.晶粒尺寸和金刚石相含量的变化表明薄膜在退火过程中发生了金刚石和非晶碳相的相互转变.可见光Raman光谱测试结果表明,不同退火时间下, G峰位置变化趋势与I_D/I_G值变化一致,说明薄膜内sp²碳团簇较大时, 非晶石墨相的有序化程度较高.退火0.5, 1.0, 1.5和2.0 h时, 电极表面进行准可逆电化学反应,而未退火和退火时间为2.5 h时电极表面进行不可逆电化学反应.退火有利于提高薄膜电极的传质效率, 退火0.5 h时薄膜电极的传质效率最高,催化氧化性能最好.较小的晶粒尺寸、 较高的金刚石相含量以及纳米金刚石晶粒的均匀分布有利于提高电极表面反应的可逆性和催化氧化性能.     

ErP5O14非晶玻璃的红外量子剪裁

研究了Er_1.0P₅O₁₄铒非晶玻璃的红外量子剪裁现象. 从吸收谱和激发光谱的计算比较中肯定了Er_1.0P₅O₁₄非晶 玻璃的1537.0 nm红外荧光为多光子量子剪裁荧光. 从Er_1.0P₅O₁₄非晶玻璃的可见和红外荧光发射光谱中发现激发²H_11/2, ⁴G_11/2和⁴G_9/2能级所导致的⁴I_13/2→⁴I_15/2量子剪裁红外荧光很强;基于自发辐射速率、无辐射弛豫速率和能量传递速率等参数的计算,对其量子剪裁机理进行了分析.发现起源于基态的强下转换能量传递{²H_11/2→⁴I_9/2,⁴I_15/2→⁴I_13/2},{⁴G_11/2→⁴I_13/2, ⁴I_15/2→²H_11/2},{⁴G_9/2→⁴F_7/2,⁴I_15/2→⁴I_13/2}和{⁴G_9/2→⁴I_13/2, ⁴I_15/2→²H_11/2}是导致Er_1.0P₅O₁₄非晶玻璃具有强的三光子和四光子量子剪裁红外荧光的原因.研究结果对改善太阳能电池效率有一定意义.     

Degradation of the transconductance of gate-modulated generation current in nMOSFET

The degradation of transconductance (G) of gate-modulated generation current I_GD in LDD nMOSFET is investigated. The G curve shifts rightward under the single electron-injection-stress (EIS). The trapped electrons located in the gate oxide over the LDD region (Q_L) makes the effective drain voltage minish. Accordingly, the G peak in depletion (G_MD) and that in weak inversion (G_MW) decrease. It is found that Δ G_MD and Δ G_MW each have a linear relationship with the n-th power of stress time (tⁿ) in dual-log coordinate: Δ G_MD ∝ tⁿ, Δ G_MD ∝ tⁿ (n=0.25). During the alternate stress, the injected holes neutralize Q_L induced by the previous EIS. This neutralization makes the effective V_D restore to the initial value and then the I_GD peak recovers completely. Yet the threshold voltage recovery is incomplete due to the trapped electron located over the channel (Q_C). As a result, G_MW only recovers to the circa 50% of the initial value after the hole-injection-stress (HIS). Instead, G_MD is almost recovered. The relevant mechanisms are given in detail.     

中频磁脉冲处理Fe52Co34Hf7B6Cu1非晶合金的正电子湮没研究

对熔体急冷法制备的非晶合金 Fe₅₂Co₃₄Hf₇B₆Cu₁ 进行了不同频率的中频磁脉冲处理, 用透射电子显微镜、穆斯堡尔谱、正电子湮没寿命谱等方法研究了处 理前后试样的微观结构及结构缺陷变化. 结果表明,经中频磁脉冲处理后,样品发生了部分纳米晶化, 晶化量随磁脉冲频率增加而增加, 当磁脉冲频率为2000 Hz时, 晶化量达33.1%; 在淬态非晶样品中, 正电子在类单空位中的湮没寿命τ₁为150.5 ps, 强度 I₁为77.7%, 在微孔洞中的湮没寿命τ₂为349.7 ps,强度I₂为22.3%; 随磁脉冲频率的增加, τ₁, τ₂值呈现减小的变化趋势, 与淬态非晶相比, I₁有所增加, I₂下降, τ₁, τ₂的平均值τ大幅降低.     

超薄栅超短沟LDD nMOSFET中栅电压对栅致漏极泄漏电流影响研究

本文研究了90nm CMOS工艺下栅氧化层厚度为1.4 nm沟道长度为100 nm的轻掺杂漏(LDD)nMOSFET栅电压V_G对栅致漏极泄漏 (GIDL)电流I_d的影响,发现不同V_G下ln (I_d/(V_DG-1.2))-1/(V_DG-1.2)曲线相比大尺寸厚栅器件时发生了分裂现象. 通过比较V_G变化下ln(I_d/(V_DG-1.2))的差值,得出V_G与这种分裂现象之间的作用机理,分裂现象的产生归因于V_G的改变影响了GIDL电流横向空穴隧穿部分所致. 随着|V_G|的变小,ln(I_d/(V_DG-1.2))曲线的斜率的绝对值变小.进一步发现不同V_G对应的ln (I_d/(V_DG-1.2))曲线的斜率c及截距d与V_G呈线性关系,c,d曲线的斜率分别为3.09和-0.77. c与d定量的体现了超薄栅超短沟器件中V_G对GIDL电流的影响,基于此,提出了一个引入V_G 影响的新GIDL电流关系式.     

DIRECT UPCONVERSION SENSITIZATION LUMINESCENCE OF Ho(0.1)Yb(5):OXYFLUORIDE VITROCERAMICS

This paper studies the upconversion luminescence phenomenon of the Ho,Yb co-doped oxyfluoride vitroceramics. There is one group of strong upconversion luminescence lines positioned at 536.5nm, 18639cm^-1; 540.5nm, 18501cm^-1; 544.0nm, 18399cm^-1, which is easily identified as the transitions of ⁵S₂→⁵I₈. There are other splendid upconversion luminescence lines, which are ⁵S₂→⁵I₇,⁵F₅→⁵I₈,⁵G₆→⁵I₈, (⁵G³G)₅ →⁵I₈,(³F³H⁵G)₄→⁵I₇,⁵G₄→⁵I₈ and (⁵G³H)₅→⁵I₈. It is also found that an interesting kind of upconversion cooperative radiation fluorescence comes from a kind of coupling state of clusters consisting of two Yb³⁺ ions.     

飞秒激光激发空气电离的阈值研究

报道在脉宽50fs—22ps，波长800nm脉冲激光作用下的空气电离阈值的研究结果.利用探测等离子体发光信号的方法，实验测量了激发空气电离所需的阈值激光强度.结果表明，当激光脉冲宽度从50fs增加到22ps时，阈值光强I_th从8.7×10¹⁴W/cm²下降到2.7×10¹³W/cm²；I_th经历了由迅速降低逐渐发展为缓慢降低的过程.在50fs—1p     

光泵重水气体产生THz激光的半经典理论分析

从半经典密度矩阵理论出发，采用三能级系统模型对光泵重水气体产生太赫兹激光进行了理论分析，求解得到了脉冲光泵重水气体分子产生太赫兹激光过程中激光信号增益系数G_s和抽运光信号被吸收系数G_p的表达式，通过迭代法对太赫兹激光信号的输出光强进行了数值计算，理论计算得到的频谱特性曲线完全符合受激Raman辐射的频谱特性，即频谱宽度较大、输出光强随抽运失谐量的改变而变化明显等特征.在脉冲激光抽运受激Raman辐射过程中，工作介质D₂O气体分子的偶极矩由于受到抽运脉冲光场的扰动发生变化，在频谱特性曲线中表现为受激辐射THz信号的谱线发生了分裂.理论计算结果与已报道的实验结果能较好地相符.     

重离子轰击Ta靶引起的多电离效应

在兰州重离子加速器国家实验室分别测量了H⁺, He²⁺, Ar¹¹⁺和Xe²⁰⁺离子轰击Ta表面过程中辐射的X射线谱, 并得到了Ta特征X射线谱中M_γ (M₃N₅)和N_αβ (M_4,5N_6,7)线的强度, 即I_γ和I_αβ. 分析结果表明, 强度比值I_γ/I_αβ 随着入射离子原子序数的增加而显著增加, 这是由于碰撞过程中Ta原子的多电离效应使M₃支壳层的荧光产额ω₃产生了显著增强.     

Superior tribological properties of an amorphous carbon film with a graphite-like structure

Amorphous carbon films with high sp² concentrations are deposited by unbalanced magnetron sputtering with a narrow range of substrate bias voltage. Field emission scanning electron microscopes (FESEMs), high resolution transmission electron microscopes (HRTEMs), atomic force microscopes (AFMs), the Raman spectrometers, nano-indentation, and tribometers are subsequently used to characterize the microstructures and the properties of the resulting films. It is found that the present films are dominated by the sp² sites. However, the films demonstrate a moderate hardness together with a low internal stress. The high hardness of the deposited film originates from the crosslinking of the sp² clusters by the sp³ sites. The presence of the graphite-like clusters in the film structure may be responsible for the low internal stress. What is more important is that the resulting films show excellent tribological properties with high load capacity and excellent wear resistance in humid atmospheres. The relationship between the microstructure determined by the deposition condition and the film characteristic is discussed in detail.     

Nanotribology of Mo–Se–C films

Transition metal dichalcogenides with a layered structure are well known for their self-lubricating properties, particularly in a vacuum or dry atmosphere. The macrotribological properties of these films have been studied extensively. However, the tribological behaviour of these films in the nanonewton load range has hardly been reported. Study of tribological properties with load in the nanonewton range is required for applications related to microelectromechanical systems or nanoelectromechanical systems. In view of the above, the hardness, surface force, friction force, etc. of Mo–Se–C films were investigated at an applied load in the nanonewton range using a nanoindenter and atomic force microscopy. The effect of carbon content, applied load and scanning speed on the friction coefficient was determined. Data pertaining to topography, lateral force and pull-off force of various surfaces are illustrated. The observed nanotribological behaviour of these films is analysed in the light of their nanohardness. The results indicate that the friction force of all the films is very low and in general dependent on surface force. However, a film having the highest carbon content exhibits the maximum friction force. With increasing carbon content of the films tested, the hardness increases and wear decreases. The above results pertain to investigations under ambient conditions.     

基片偏压对MCECR溅射硬碳膜特性的影响

采用封闭式电子回旋共振(MCECR)氩等离子体溅射碳靶的方法在硅片上沉积了高质量的硬碳膜, 膜层厚度约40 nm. 使用X射线光电子能谱仪(XPS)和高分辨率透射电子显微镜(HRTEM)分析了碳膜结构,并用POD摩擦磨损仪测试了碳膜的摩擦磨损特性,用纳米压入仪测试了碳膜的纳米硬度.详细研究了基片偏压对碳膜的结构、摩擦磨损特性以及纳米硬度的影响,得到了最佳基片偏压.     

Microstructure and tribological behavior of pulsed laser deposited a-CNx films

The a-CN_x films were deposited onto high-speed steel substrate by pulsed laser deposition at different nitrogen pressures. The tribological properties of the films in humid air and in vacuum were investigated using a ball-on-disk tribometer under various loads. The composition, microstructure and morphology of the films, wear tracks and paired balls were characterized by energy dispersive X-ray analysis (EDXA), X-ray photoelectron spectrum (XPS), Raman spectroscopy and scanning electron microscopy (SEM). With increasing the deposition pressure, the fraction of sp³ C bond reduces, the fraction of trapped nitrogen increases and the friction coefficient of the films declines both in humid air and vacuum. The friction coefficient of a-CN_x film decreases with increasing normal load. The tribological performances of the films in humid air are better than those of in vacuum. A transferred graphite-like tribo-layer is observed from a-CN_x film to the paired ball for both environments.     

铟锡氧化物薄膜表面等离子体损耗降低的研究

本文采用直流磁控溅射方法在普通浮法玻璃基底上制备了立方多晶铁锰矿结构的铟锡氧化物(indium tin oxide, ITO)薄膜,并对其进行了结晶性、表面粗糙度、紫外-可见吸收光谱、折射率、介电常数及霍尔效应的测试.研究了溅射时基底温度的改变对于ITO薄膜的光电、表面等离子体性质的影响.随着基底温度由100?C升高至500?C,其光学带隙(3.64—3.97eV)展宽,减少了电子带间跃迁的概率,有效降低了ITO薄膜的光学损耗.与此同时,对应ITO薄膜的载流子浓度(4.1×10~(20)-—2.48×10~(21)cm~(-3))与迁移率(24.6—32.2 cm~2·V~(-1)·s~(-1))得到提高,电学损耗明显降低.     

The electrochemical and mechanical properties of Ti incorporated amorphous carbon films in Hanks’ solution

Ti incorporated amorphous carbon (a-C) films with variant Ti contents were prepared by the unbalanced magnetron sputtering process. Scanning electron microscopy, ultraviolet Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy were used to characterize the microstructure of a-C films. The hardness and lubricated tribological properties were assessed using nanoindentation and ball-on-disk tribometer. As the Ti content in a-C films increases from 0 to 15.2 at.%, the sp³ volume fraction, the internal stress and the hardness of the films decreases gradually, while the disorder of sp² bond increases. The electrochemical tests reveal that the a-C films with lower than 1.5 at.% Ti possess good corrosion resistance in Hanks’ solution, while the a-C film with 15.2 at.% Ti is susceptible to crevice corrosion. The reduced friction of the a-C films is due to the sp² bonded film surface and boundary lubrication of the Hanks’ solution. The a-C film with 3.1 at.% Ti exhibits the best wear resistance in Hanks’ solution among the studied films.     

脉冲偏压电弧离子镀Cr-O薄膜结构及光学性能研究

采用脉冲偏压电弧离子镀技术在单晶硅基片及石英玻璃上制备了一系列均匀透明的Cr-O薄膜. 用场发射扫描电子显微镜、X射线衍射仪、X射线光电子谱、纳米压痕仪、紫外可见光分光光度计等方法对薄膜的表面形貌、膜厚、相结构、成分、元素的化学价态、硬度和光学性能等进行表征, 主要研究了偏压幅值对薄膜结构和性能的影响. 结果表明, 施加偏压可使薄膜的沉积质量明显提高, 其相结构由非晶态转变为晶体态, 并随着偏压幅值的增加, 由Cr₂O₃相向CrO相转变; 薄膜的硬度先增大后减小, 当偏压为-300 V时, 硬度达到最大值24.4 GPa; 薄膜具有良好的透光率, 最高可达72%; 当偏压为-200 V时, 薄膜的最大光学帯隙为1.88 eV.     

Perpendicularly oriented barium ferrite thin films with low microwave loss,prepared by pulsed laser deposition

Barium ferrite(Ba M) thin films are deposited on platinum coated silicon wafers by pulsed laser deposition(PLD).The effects of deposition substrate temperature on the microstructure,magnetic and microwave properties of Ba M thin films are investigated in detail.It is found that microstructure,magnetic and microwave properties of Ba M thin film are very sensitive to deposition substrate temperature,and excellent Ba M thin film is obtained when deposition temperature is 910℃ and oxygen pressure is 300 m Torr(1 Torr = 1.3332×10~2Pa).X-ray diffraction patterns and atomic force microscopy images show that the best thin film has perpendicular orientation and hexagonal morphology,and the crystallographic alignment degree can be calculated to be 0.94.Hysteresis loops reveal that the squareness ratio(M_r/M_s) is as high as 0.93,the saturated magnetization is 4004 Gs(1 Gs = 10~4T),and the anisotropy field is 16.5 kOe(1 Oe = 79.5775 A·m~(-1)).Ferromagnetic resonance measurements reveal that the gyromagnetic ratio is 2.8 GHz/kOe,and the ferromagnetic resonance linewith is108 Oe at 50 GHz,which means that this thin film has low microwave loss.These properties make the Ba M thin films have potential applications in microwave devices.     

Effect of Chromium on Structure and Tribological Properties of Hydrogenated Cr/a-C:H Films Prepared via a Reactive Magnetron Sputtering System

Hydrogenated Cr-incorporated carbon films(Cr/a-C:H) are deposited successfully by using a dc reactive magnetron sputtering system.The structure and mechanical properties of the as-deposited Cr/a-C:H films are characterized systematically by field-emission scanning electron microscope,x-ray diffraction,Raman spectra,nanoindentation and scratch.It is shown that optimal Cr metal forms nanocrystalline carbide to improve the hardness,toughness and adhesion strength in the amorphous carbon matrix,which possesses relatively higher nano-hardness of 15.7GPa,elastic modulus of 126.8 GPa and best adhesion strength with critical load(L_c) of36 N for the Cr/a-C:H film deposited at CH_4 flow rate of 20 sccm.The friction and wear behaviors of as-deposited Cr/a-C:H films are evaluated under both the ambient air and deionized water conditions.The results reveal that it can achieve superior low friction and anti-wear performance for the Cr/a-C:H film deposited at CH_4 flow rate of 20 sccm under the ambient air condition,and the friction coefficient and wear rate tested in deionized water condition are relatively lower compared with those tested under the ambient air condition for each film.Superior combination of mechanical and tribological properties for the Cr/a-C:H film should be a good candidate for engineering applications.     

Effect of boron ion implantation on the structural, optical and electrical properties of ZnSe thin films

Zinc Selenide (ZnSe) thin films were deposited onto well cleaned glass substrates using vacuum evaporation technique under a vacuum of 3×10⁻⁵ mbar. The prepared ZnSe samples were implanted with mass analyzed 75 keV B⁺ ions at different doses ranging from 10¹² to 10¹⁶ ions cm⁻². The composition, thickness, microstructures, surface roughness and optical band gap of the as-deposited and boron-implanted films were studied by Rutherford backscattering (RBS), grazing incidence X-ray diffraction, Atomic force microscopy, Raman scattering and transmittance measurements. The RBS analysis indicates that the composition of the as-deposited and boron-implanted films is nearly stoichiometric. The thickness of the as-deposited film is calculated as 230 nm. The structure of the as-deposited and boron-implanted thin films is cubic. It is found that the surface roughness increases on increasing the dose of boron ions. In the optical studies, the optical band gap value decreases with an increase of boron concentration. In the electrical studies, the prepared device gave a very good response in the blue wavelength region.