Lake Shore Cryotronics CRX-6.5K, Руководство пользователя

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20 CHAPTER 2: System Overview
Model CRX-6.5K Probe Station
2.3.4 Optical Fiber
Assembly Optical fiber compatible probe arms can be ordered as PS-FOA options. The option is
configurable to accommodate a variety of fiber types and applications. Each option
includes a probe arm and base with vacuum feedthrough and mount. Lake Shore
offers the choice of several optical fibers, or customers can install their own fibers in
the field. Contact your Lake Shore sales representative for more information.
2.3.5 Sample Holders Sample holders attach to the top of the sample stage to provide a good mounting
surface for the wafer or device under test. They can be removed easily to facilitate
careful sample mounting. One grounded sample holder is included with the system,
but it can be interchanged with any of the optional sample holders (as long as the
appropriate feedthrough wiring option is installed for coaxial/triaxial). It is often
desirable to order more than one holder so one sample can be mounted while another
is being measured.
Different models are optimized for different electrical measurement applications.
All of the holders are thermally conductive so the sample temperature remains close
to the sample stage temperature, but there are some trade-offs between thermal
conductivity and electrical characteristics. TABLE 2-1 shows the temperature
gradients that are typical between the sample stage temperature sensor and the top
of each sample holder. The gradients are given for base temperature, which is the
worst case; gradients are smaller at higher temperatures.
2.3.5.1 Grounded Sample Holders
Grounded holders are the most common type and are referred to as grounded
because the back side of the sample is held at system ground. They are recommended
for routine measurements, especially when samples are patterned on highly
insulating substrates or leakage current is not a concern. They are constructed out of
solid metal, making them the most thermally and electrically conductive. The
smallest thermal gradient between the sample stage and sample mounting surface
can be achieved with the standard SH-1.25-G grounded sample holder. The
maximum operating temperature is 350 K when using the grounded sample holder.
2.3.5.2 Isolated Sample Holders
Isolated holders have a nonconductive sample mounting surface that electrically
isolates the sample from system ground. They are recommended for measuring
samples with electrically conductive features on the back side. They are constructed
similarly to grounded holders, but have a sapphire disk attached to the top surface.
The sapphire is an excellent electrical insulator and retains good thermal
conductivity at cryogenic temperatures. Moderate thermal gradients between the
sample stage and sample mounting surface should be expected. The maximum
operating temperature is 350 K.
Sample holder type Sample holder model Maximum sample size
Temperature
difference at 4.5 K*
Maximum
temperature
Grounded SH-1.25-G 32 mm (1.25 in) 0.1 K to 0.2 K
350 K
Isolated SH-1.25-I 32 mm (1.25 in) ~1 K
Coaxial SH-1.25-C 32 mm (1.25 in) ~1 K
Triaxial SH-1.25-T 32 mm (1.25 in) ~1 K to 2 K
Grounded SH-2.00-G 51 mm (2 in) 0.1 K to 0.2 K
Coaxial SH-2.00-C 51 mm (2 in) ~1 K
Triaxial SH-2.00-T 51 mm (2 in) ~1 K to 2 K
*Temperature difference between the top of the sample holder and the sample stage temperature sensor. Additional
temperature difference can be expected between the sample and sample holder, depending on mounting technique
and experimental heat load.
TABLE 2-1 Sample holder summary