Quartz Crystal Thickness Monitor Research Articles

Experimental set-up for irradiation of solid H2 and D2 with charged particles of keV energies

An experimental facility was built where films of solid deuterium (and hydrogen) may be made with known thickness and irradiated with pulsed beams of electrons (up to 3 keV) and light ions (up to 10 keV). Films are made on a target plate held at 2.5–3 K. Film growth rate is calibrated with a quartz crystal film thickness monitor. The target plate, which can be heated so that films are removable by evaporation, may be used both as a calorimeter and as a beam current collector. Methods for measurement of secondary electron emission coefficients were developed, and preliminary measurements were made with electrons and hydrogen ions. For electron bombardment, the secondary electron emission coefficient of solid deuterium was much smaller than one. It was shown possible to use the set-up to study beam desorption of very thin films. Furthermore the set-up could be used for measuring the energy-reflection coefficient γ (i.e. the fraction of beam energy reflected from the target) for protons impinging on a heavy target material by using the target as a calorimeter.

Hole Formation in Gold Films

During recent experiments on Au films, a qualitative correlation between hole formation and deposition rate was observed. These early studies were concerned with films 80 to 1000A thick deposited on glass at -185°C and annealed at 170°C. In the present studies this earlier work was made quantitative. Deposition rates varying between 5 and 700 A/min were used. The effects of deposition rate on hole density for two films 300 and 700A thick were investigated.Au was evaporated from an outgassed W filament located 10 cm from a glass microscope slide substrate and a quartz crystal film thickness monitor. A shutter separating the filament from the substrate and monitor made it possible to obtain a constant evaporation rate before initiating deposition. The pressure was reduced to less than 1 x 10-6 torr prior to cooling the substrate with liquid nitrogen. The substrate was cooled in 15 minutes during which the pressure continued to drop to the mid 10-7 torr range, where deposition was begun.

Measurement of Vapor Pressures and Backstreaming with a Mass Spectrometer Calibrated against a Quartz Crystal Thickness Monitor

Oil backstreaming is directly measured by detection of the free molecular flow coming from the baffle to be examined. A quadrupole mass spectrometer with open-type ion source is used. For absolute calculation it is first exposed to a panel covered with pump fluid at defined temperature. Simultaneously the evaporation rate is measured by a quartz crystal thin film monitor. The mass spectrometer gives the relative contribution of different constituents to the total vapor pressure as measured by the quartz monitor. The detection limit of the quartz monitor corresponds to vapor pressures in the 10−9 Torr range. For the correct extrapolation of the mass spectrometer reading to far lower levels, the dependence of the molecular beam density on the particle velocity has to be considered. Interference by a background of vapor coming from any other source is excluded by a shutter between the detector and the vapor source to be investigated.

Application of a quartz crystal thickness monitor in the continuous measurement of thickness of evaporated and sputtered metal films : R. Chabicovskyet al. Vakuum-Technik19 (5), May (1970), p. 101. (In German.)

Application of a quartz crystal thickness monitor in the continuous measurement of thickness of evaporated and sputtered metal films : R. Chabicovskyet al. Vakuum-Technik19 (5), May (1970), p. 101. (In German.)

Density of Thin Films of Vacuum Evaporated Metals

IT is well known that the density of a material depends on its method of preparation and subsequent treatment. Values of the densities of bulk materials treated in various ways are given in reference tables1. Increasing use is, however, being made of materials in the form of thin evaporated films, and in some experiments, such as those involving measurements of transmission or energy loss with atomic particles, the superficial density of the film is a more significant parameter than its linear thickness. It is not always possible to measure the superficial density sufficiently accurately by direct weighing. A knowledge of the density of the evaporated material is needed for the superficial density of the film to be calculated from its linear thickness, measured, for example, by multiple beam interferometry2–4. Observations5 on silver films in which the mass of silver was estimated by a chemical colorimetric method accurate to 3 per cent gave agreement between the density of the film and the bulk density. For aluminium, however, the oscillating quartz crystal thickness monitor described by Lawson6 gave an observed thickness sensitivity some 4 per cent greater than the theoretical sensitivity. The thickness sensitivity, measured as the shift in frequency/unit linear film thickness, is directly proportional to the density of the evaporated material. The early measurements by Kahlbaum7 seem to have been made with massive samples recast from vacuum distilled material. We report here the results of direct determinations of the density of some metallic films. The linear thicknesses were determined by multiple beam interferometry and the superficial densities were measured gravimetrically.