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 pa rameters, we describe techniques which have been developed to accurate ly set, maintain, and measure the temperature of a small sample (typic ally a single-crystal disk of about 1 cm in diameter and 1 mm thick) i n a strongly nonisothermal surrounding in ultrahigh vacuum, such as re quired by surface science experiments, in the temperature range from a t least 6.5 K up. The resettability and resolution are 30-70 mK and th e absolute error is estimated as about 0.7 K at 10 K and about 1.5 K a t 100 K. Controlled linear heating with rates from 10(-2) to 50 K/s an d 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 o vershoot can be carried out in this whole cryogenic range.