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在许多晶体中，电偶极子[1]以首选的红色方向排列，形成一个带电表面。在热膨胀期间，表面电荷移动，从而带来热释电效应。当光闸开启（使温度增加）或关闭（使温度降低）时，会出现极性相反的电流峰值。 In many crystals, electric dipoles are ordered in a preferreddirection, resulting in a charged surface. During thermal expan-sion, the surface charges shift, which causes the pyroelectriceffect, a current peak of the opposite polarity when the light shut-ter is opened (which increases temperature) and closed (whichdecreases temperature).   在测量光电导率时，使用特氟纶基底可以避免上述情况的发生。因为该材料可以存储电荷[2]，在热膨胀期间，存储的电荷也将发生移动，产生与热释电效应相似的效应。图3给出光电导率测量技术试验结果。 Avoid using Teflon substrates when measuring photoconduc-tivity—this material stores charges, which will also shift duringthermal expansion, producing an effect similar to the pyroelectriceffect. Figure 3 illustrates an experimental photoconductivitymeasurement technique.
  图3: 在SF₆气体中对包含晶体（尺寸：1mm）的C₆₀光电导率进行测量。由于晶体的各向异性，对绿色激光(532nm)的响应要远远大于对与晶体轴[3](c)正交的非极化光(E)的响应。 Figure 3: Photoconductivity measurement of a C60containing crystal (1mm insize) under SF6atmosphere. Due to the anisotropy of the crystal, theresponse to green laser light (532nm) is much stronger for apolarization of the light (E) perpendicular to the crystal axis (c).      了解更多信息
     要想了解有关6517A型静电计/高阻表[4]或者吉时利其他系列数字源表的更多信息，请点击http://www.keithley.com.cn/products/localizedproducts/highresistance/6517a，或者联系吉时利公司：全国免费电话800-810-1334手机用户请拨打440-650-1334。 登录吉时利官方微博（http://weibo.com/keithley）与专家进行互动。

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[1] 电偶极子http://www.keithley.com.cn/products/localizedproducts/localizedproducts/2004_china_catalog.pdf [2] 4205-PG2型双通道脉冲发生器http://www.keithley.com.cn/semi/4200scs/4205 [3] 晶体轴http://www.keithley.com.cn/products/localizedproducts/localizedproducts/2004_china_catalog.pdf [4] 6517A型静电计/高阻表http://www.keithley.com.cn/products/localizedproducts/highresistance/6517a