Piezoelectric quartz crystal microbalance (PQCMB) for sorption studies under dynamic conditions

Abstract

Construction of the measuring cell and of the auxiliary electric and electronic equipments of a PQCMB is described. The cell is designed for equilibrium and kinetic studies on the thin solid (metallic) layer/gas interface with inert carrier gas (dynamic conditions). Special attention is given to the temperature constancy: the auxiliary equipment of PQCMB is thermostated to within ±0.5°C, the cell to within ±0.005°C. Under these conditions a short-term stability of the frequency better than ±0.01 Hz is obtained, at a nominal frequency of 5.023 MHz, i.e., better than ±2 ppb; the weighing limit is about 5×10−11 g. The long-term stability attained under the same conditions is about ±0.02 Hz. The conditions for using the PQCMB in UHV-surface studies within 80 and 400 K are briefly discussed.