A simple apparatus for film thickness measurements

Thermal and intrinsic stresses in single-crystal nickel films

“…High-energy electron bombardment of the substrate was employed prior to and/or during evaporation-a procedure which has been shown to improve the epitaxial quality of the resultant film [ 5 ] . The thickness of the evaporated films, ranging from 500 to 3000 A, was measured using a multiple-beam Fizeau interferometric system [6]. The films were circular in shape with a diameter of 5 mm.…”

“…where Y f is Young's modulus for the film. Equation (6) indicates that the thermal stress can be of either sign, and can be controlled by a judicious choice of substrate material and deposition temperature. Since the thermal expansion coefficients of NaF, LiF and NaCl are larger than that of the nickel [ 111, the thermal stress measured at room temperature is thus compressive (negative).…”

“…However for a MgO substrate the stress is tensile (positive) since the thermal expansion coefficient of MgO is smaller than that of nickel (see table 1). It should be noted that equation (6) has been used to calculate the thermal stress in single-crystal nickel films and the results are depicted in table 1. Values of the coefficients of thermal expansion of nickel (aNi = 13.4 x O C -' ) and the substrates used were taken from reference [ l l ] and the value of Young's modulus of nickel ( Y N i = 2.2 X lo'* dyn cm-') was taken from reference [12].…”