气相生长硒化镉单晶体的生长速度研究

以晶体生长理论为基础，计算了气相提拉生长CdSe晶体时的生长速率。结果表明用提拉法气相生长CdSe晶体时，晶体的气相生长速率将会随着时间的延长以指数关系快速的趋近于提拉速度，以后不再变化。由此，在选定温场的前提下，对CdSe单晶体的气相生长速度进行了优化，确定了3mm／d的生长速度，得到了平界面生长的尺寸为Ф20mm×30mm，电阻率高达10^9Ω·cm，且未观察到深能级陷阱的优质CdSe大单晶体.     

霍尔效应的地下位移三维测量方法研究

当霍尔传感器与磁钢之间的相对位置变化时,霍尔传感器感受到的磁感应强度也随之变化,从而导致传感器的输出电压改变.采用三个霍尔传感器组成传感器阵列,建立三维笛卡儿坐标系.通过测量传感器的输出电压并结合一定的算法,可计算出某一时刻磁钢的三维坐标.地下土体的变形会改变霍尔传感器与磁钢之间的相对位置.在得到磁钢新的三维坐标之后,通过几何运算得出位移的大小.     

新一代霍尔效应智能磁强计的研究

智能磁强计是在设计上采用单片机和数字电位器，替代传统的机械电位器的基础上，研发出的一种基于霍尔效应的新型智能化磁场强度测量仪器。从根本上解决机械电位器因接触不良而产生的噪声、漂移等问题。实践证明：该仪器具有测量范围宽，测量精度高，校准常数调节和零点调节实现智能化，换能器更换方便和使用简单等特点，且具有较好的线性度＇其测量误差均在0.5％以内。已取得了较好的经济效益，应用推广前景广阔。     

霍尔效应测量大电流的理论探讨

大电流、大电压的测量一直是困扰工程测量学的难题。本文着重探讨了霍尔效应应用于测量大电流的工作原理、数学推算以及应用中需要注意的几个问题。力图寻求将新技术用于工程测量中难点问题的理论依据。     

基于霍尔效应的新型多功能数字高斯计设计

本方案利用相关电子元器件自制新型多功能高斯计,然后用已有高斯计进行标定,最终准确测量及数字显示待测的磁感应强度,绘制的较为简单的磁滞曲线,并实现其它相应功能。采用的是霍尔效应法对磁场进行测量,其物理学的理论支持是霍尔效应。探测电路通过霍尔效应把难以测量的磁信号转变为易于处理的电信号。     

基于霍尔效应的印刷机能耗检测方法研究

目的采用霍尔元件法搭建印刷机群能耗数字化检测平台。方法通过建立印刷机能耗指标模型框架体系,形成以总耗电量指标、均值类指标、耗电比例类指标等为主的印刷机耗电评价标准,完善能耗评价准则。采用灵敏度高、稳定性好的霍尔元件作为能耗检测元件,并分析霍尔效应、磁平衡式电流和电压霍尔传感器的检测电路。采用伏安法功率测量方式分别检测各负载电路的电流与电压,通过A/D转换模块实现检测数据数字化,并通过硬件控制核心对采集的数字信号进行运算、输出和显示,采用CAN总线实现硬件控制系统与上位机之间数字信息交互。结果搭建了印刷机群能耗数字化检测系统平台,实现了外围设备与上位机间的数据交互,实现了印刷机群以数据为核心,通过能耗检测、能效分析、能源成本控制以及能源指标优化,提高了能源利用效率。结论能耗检测的实现既能减少冗余电量损耗,又有利于监测电路稳定性,利用霍尔元件法实现印刷机群能耗检测的方法是可行的。     

交流量子化霍尔效应及其应用

利用量子化霍尔效应实现的直流电阻自然基准已经得到广泛应用,国际计量委员会给出了量子化霍尔电阻的国际推荐值作为各国统一电阻量值的依据。为了保持单位的一致性,交流阻抗的单位亦应溯源到量子化霍尔电阻,国际上因此开展了交流量子化霍尔电阻的研究。目前从交流量子化霍尔电阻传递出电容量值的不确定度已达到１～２×１０－７,可以基本满足实际工作中交流阻抗单位准确度的需要。要进一步提高交流量子化霍尔电阻的准确度,则需要在一些基础性的研究方面作更为深入的工作。     

我与『量子化霍尔效应』

我自1967年来到中国计量科学研究院(以下简称"计量院"),迄今已41年.这41年的一大半时间是和"量子化霍尔效应"一起度过的.至今已经形影不离相处了26年.     

氮化铁薄膜中反常霍尔效应的研究

通过磁控溅射方法制备了氮含量不同的氮化铁薄膜,观察到随着氮含量的增加,薄膜的导电机制从金属到半导体的转变。霍尔电阻的测量表明在高电阻区域反常霍尔电阻率与纵向电阻率的标度律为线性,即反常霍尔效应遵循斜散射机制,但相应的反常霍尔电导率与纵向电导率的关系不总是线性。     

双温区生长CdSe单晶及其红外表征

硒化镉晶体是一种很有前途的室温核辐射探测器半导体材料,实验采用改进的双温区气相垂直提拉法成功的生长了Φ15mm×40mm,电阻率为107～108(Ω·cm)量级的硒化镉单晶体.对生长的硒化镉单晶体(110)解理晶片进行XRD、红外透过测试,结果显示:硒化镉单晶体完整性好,红外透过率＞62%,表明用二步提纯,在具有较好温度梯度的双温区炉中生长晶体,能有效地控制杂质、缺陷浓度和晶体的化学配比.     

Magnetostriction of HTSC single crystals

We have measured the sample length change of HTSC single crystals in the superconducting state in a magnetic field. The magnetic field was applied parallel to the crystallinec-axis direction and was swept at a constant rate of 10 mT/s up to 6 T. The sample length change was measured along theab-plane direction, i.e., perpendicular to the field. We have found for the Bi₂Sr₂CaCu₂O₈ single crystals that the relative sample length change (L/L) is extraordinarily large for a superconductor, on the order of 10^–4. For the case of (La_1–x Sr _x )₂CuO₄, the amount of magnetostriction was not as large as for the Bi system, but the magnetostriction curves had many similarities. For both compounds, a relaxation phenomenon was observed when the field sweep was suspended at a certain field value. These observations are discussed in relation to flux line pinning.     

Hall Effect in Bulk‐Doped Organic Single Crystals

The standard technique to separately and simultaneously determine the carrier concentration per unit volume (N , cm^?3) and the mobility (μ) of doped inorganic single crystals is to measure the Hall effect. However, this technique has not been reported for bulk‐doped organic single crystals. Here, the Hall effect in bulk‐doped single‐crystal organic semiconductors is measured. A key feature of this work is the ultraslow co‐deposition technique, which reaches as low as 10^?9 nm s^?1 and enables us to dope homoepitaxial organic single crystals with acceptors at extremely low concentrations of 1 ppm. Both the hole concentration per unit volume (N , cm^?3) and the Hall mobility (μ_H) of bulk‐doped rubrene single crystals, which have a band‐like nature, are systematically observed. It is found that these rubrene single crystals have (i) a high ionization rate and (ii) scattering effects because of lattice disturbances, which are peculiar to this organic single crystal.     

Conduction mechanism of metal-free phthalocyanine single crystals as a function of temperature

Metal-free phthalocyanine (H₂Pc) single crystals grown by vacuum sublimation were investigated for their conductivity (both in dark and light). The investigations consisted of dark- and photo-current variations with (i) applied electric field and (ii) temperature. The applied electric field ranged from 0·8 kV/cm to 6 kV/cm. The temperature range was from 300°K to around 570°K. The crystals were found to be photoconductive. Based on activation energies calculated from photoconductivity due to temperature dependence, an energy level scheme for H₂Pc single crystals is proposed. The model consists of two trapping levels within the forbidden gap — one at 0·4 eV below the conduction band edge from which electrons are thermally excited into the conduction band and the other acts as recombination centre at 0·3 eV above the valence band edge. The band gap is calculated to be 1·4 eV. Comparative study of the proposed model with that of earlier investigations on the same crystals of the H₂Pc is in good agreement, thereby indicating that H₂Pc is thermally stable even at relatively higher temperature as semiconductor.     

预时效时CuAlNi单晶相变温度的影响

根据有序化理论,提出预时效概念,并用无析出物形成的预时效处理研究了Ｃｕ－１３．４Ａｌ－４．０Ｎｉ单晶相孪温度承时效工艺的变化,结果ＤＳＣ和偏光金相分析探讨了预时效与时效的界限,淬冷状态的Ｃｕ－Ａｌ－Ｎｉ单晶其相变温度可以根据需要进行预时效处理,经预时效后,其Ｍｓ为淬冷态的Ｍｓ＋０～７０℃,Ａｓ为淬冷态的Ａｓ＋０～９０℃可调,预时效温度应为淬冷态的Ｍｓ＋１００－２００℃,经过预时效的合金在马氏体状态     

Domain patterns on ferroelectric Rh:BaTiO3 single crystals

Single crystal growth and domain structure of Rh:Barium titanate (BaTiO₃) have been investigated. Rh doping in BaTiO₃ is effective for the growth of bulk crystals without twin formation. Atomic force microscope (AFM) and optical microscope studies reveal the formation 180° and 90° domains on the grown crystals. It has been observed that the complex 180° domain structure with typical size of around 20 μm exists in the c-domain of {0 0 1} face of Rh doped BaTiO₃ crystals.