Techniques for attainment, control, and calibration of cryogenic temperatures at small single-crystal samples under ultrahigh vacuum

On the basis of detailed considerations of the relevant effects and parameters, we describe techniques which have been developed to accurately set, maintain, and measure the temperature of a small sample (typically a single-crystal disk of about 1 cm in diameter and 1 mm thick) in a strongly nonisothermal surrounding in ultrahigh vacuum, such as required by surface science experiments, in the temperature range from at least 6.5 K up. The resettability and resolution are 30-70 mK and the absolute error is estimated as about 0.7 K at 10 K and about 1.5 K at 100 K. Controlled linear heating with rates from 10^-2 to 50 K/s and high constancy (deviations below 0.1 K up to 5 K/s and below 0.5 K up to 50 K/s), and stepwise heating (>100 K/s) without measurable overshoot can be carried out in this whole cryogenic range.