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测量系统的温度变化将带来热膨胀，从而改变电容[1]，在电流中引入额外噪声。如果在环境温度（不加热也不冷却）下进行测量，在测量期间系统温度一般是足够稳定的。不过，如果需要与温度有关的测量，那么温度稳定性应当优于0.1K。 Temperature changes in the measurement system cause thermal expansions and, therefore, changing capacitances, introducing additional noise in the current. If measurements are performed atambient temperature without additional heating or cooling, thesystem temperature is usually sufficiently stable during measure-ment. However, if temperature-dependent measurements are nec-essary, the temperature stability should be better than 0.1K.   考虑到光吸收问题，在测量光电导率时，必须使样本和测量系统加热最小化。这要求使用具有良好热导率[2]的材料。对于这种应用，最好的选择是使用蓝宝石基底和铜电极来安装样本，如图2所示。除了具有出众的体积电阻率以及良好的抗吸水性表面，蓝宝石还具有优良的热导率，而且在大部分光谱范围内都不会吸收光波。为了使系统吸收的热量最小化，要小心谨慎，只对样本进行照明(例如，要聚焦光线或使用激光束)，不要包围电极和屏蔽层[3]。系统加热可能带来电流的增加，这与光电导率测量非常相似。 To measure photoconductivity, it’s essential to minimizeheating of the sample and measurement system due to lightabsorption. This requires using materials with good heat conduc-tivity. For this application, the best choice is to use a sapphiresubstrate and copper electrodes to mount the sample, as shown inFigure 2. In addition to its excellent volume resistivity and asurface with good resistance to water absorption, sapphire hasgood thermal conductivity and doesn’t absorb light over a widespectral range. To minimize the amount of heat the systemabsorbs, exercise care to illuminate only the sample (e.g., byfocusing the light or using a laser beam), not the surroundingelectrodes and shields. System heating can cause a rise in cur-rent, much as it does in photoconductivity measurements.      了解更多信息
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[1] 电容http://www.keithley.com.cn/news/prod110121 [2] 半导体器件实验室http://www.keithley.com.cn/re/sdl [3] 屏蔽层http://www.keithley.com.cn/llm/a/17.html [4] 6517A型静电计/高阻表http://www.keithley.com.cn/products/localizedproducts/highresistance/6517a