高值电阻( 高达1017W)的常用测量方法是施加恒定电压[1]，然后测量产生的电流。通常，使用的电压越高，测量精度也越高。不过，在小型晶体（尺寸<1mm ）上施加的电压电平受到接触电极之间空气电子击穿的限制（1kV/mm 电场）。在较高电压测量晶体电阻的方法有两个。一个方法是在高真空条件下进行测量，这需要10-4 以下的气压。第二个方法是在轻微过压下（1–2 bar ）使用具有较高击穿阈值[2]的惰性气体( 如SF6) 。使用高真空的优势是实际上没有击穿限制。不过，同高真空测量相比，使用惰性气体更容易控制样本温度，因为在高真空条件下，没有可用的传导热量气体。 High resistances (up to 1017Ω) are usually measured by applyinga constant voltage, then measuring the resulting current. In gen-eral, using a higher voltage allows making a more accuratemeasurement. However, the level of voltage that can be appliedto small crystals (those <1mm in size) is limited by the electrical breakdown of air between the contacting electrodes at an electri-cal field of 1kV/mm.There are two ways to measure these crystals at higher volt-ages. The first technique is to measure under high vacuum condi-tions, which requires a pressure level lower than 10–4 mbar. Thesecond approach is to use an inert gas with a higher breakdown threshold (such as SF6) under a slight overpressure (1–2 bar).The advantage of using high vacuum is that there’s virtually no breakdown limit. However, when using an inert gas, it’s mucheasier to control the temperature of the sample than when meas-uring in high vacuum, where no gas is available to transfer heat.
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[1] 2510精密温控源表http://www.keithley.com.cn/products/dcac/currentvoltage/?mn=2510
[2] 电路/基础电子实验室http://www.keithley.com.cn/re/cel
[3] 6517A型静电计/高阻表http://www.keithley.com.cn/products/localizedproducts/highresistance/6517a | 
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