Sakai C, Takeda S N, Daimon H
Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0101, Japan.
Rev Sci Instrum. 2013 Jul;84(7):075103. doi: 10.1063/1.4812336.
We have developed the new in situ electrical-conductivity measurement system which can be operated in ultrahigh vacuum (UHV) with accurate temperature measurement down to 20 K. This system is mainly composed of a new sample-holder fixing mechanism, a new movable conductivity-measurement mechanism, a cryostat, and two receptors for sample- and four-probe holders. Sample-holder is pushed strongly against the receptor, which is connected to a cryostat, by using this new sample-holder fixing mechanism to obtain high thermal conductivity. Test pieces on the sample-holders have been cooled down to about 20 K using this fixing mechanism, although they were cooled down to only about 60 K without this mechanism. Four probes are able to be touched to a sample surface using this new movable conductivity-measurement mechanism for measuring electrical conductivity after making film on substrates or obtaining clean surfaces by cleavage, flashing, and so on. Accurate temperature measurement is possible since the sample can be transferred with a thermocouple and∕or diode being attached directly to the sample. A single crystal of Bi-based copper oxide high-Tc superconductor (HTSC) was cleaved in UHV to obtain clean surface, and its superconducting critical temperature has been successfully measured in situ. The importance of in situ measurement of resistance in UHV was demonstrated for this HTSC before and after cesium (Cs) adsorption on its surface. The Tc onset increase and the Tc offset decrease by Cs adsorption were observed.
我们开发了一种新的原位电导率测量系统，该系统可在超高真空（UHV）中运行，能精确测量低至20 K的温度。该系统主要由一种新型样品架固定机构、一种新型可移动电导率测量机构、一个低温恒温器以及用于样品架和四探针架的两个接收器组成。通过使用这种新型样品架固定机构，可将样品架紧紧地压靠在与低温恒温器相连的接收器上，以获得高导热性。使用这种固定机构，样品架上的测试片已被冷却至约20 K，而在没有这种机构的情况下，它们只能被冷却至约60 K。使用这种新型可移动电导率测量机构，在基板上成膜或通过解理、闪蒸等方法获得清洁表面后，能够将四个探针接触到样品表面以测量电导率。由于样品可以在直接连接有热电偶和/或二极管的情况下进行转移，因此可以进行精确的温度测量。在超高真空下对铋基氧化铜高温超导体（HTSC）单晶进行解理以获得清洁表面，并成功地原位测量了其超导临界温度。对于该HTSC，证明了在其表面吸附铯（Cs）之前和之后在超高真空下原位测量电阻的重要性。观察到由于Cs吸附导致的Tc起始温度升高和Tc偏移温度降低。
