Optical thickness monitor for thin film deposition.

A monitoring technique is presented for controlling the deposition of dielectric films, based on periodic comparison of the reflectances of the coated and uncoated regions of a substrate. The device described is very simple in construction and operating principles; with some refinements it gives extremely high sensitivity for very thin (

Measuring the refractive index and thickness of thin transparent films: method.

A new method is described for the determination of refractive index of transparent films on transparent substrates based on the observation of an interference pattern in the light scattered by the film. The pattern consists of a series of bright rings caused by multiple reflections inside the film; when the film index is lower than the substrate index, a measurement of the diameters of two rings uniquely determines both film index and thickness. Accuracies of 1 part in 10(3) for the refractive index and 1 part in 10(2) for the thickness are obtained. Examples of application to films of several thermally evaporated materials are given.

Flash evaporation of compounds with a pulsed-discharge CO(2) laser.

Pulsed laser radiation at 10.6 microm has been used to evaporate a number of compounds chosen for their difficulty of evaporation with conventional techniques. An average laser power of 8 W, pulsed at 50 Hz with a 1-msec duration, has been found sufficient to obtain useful evaporation rates for Al(2)O(3) and other highly refractory materials. For easily decomposed materials such as CdS and ZnS, comparison of cw and pulsed evaporation through measurement of optical and photoconductive film properties consistently indicates higher stoichiometry in pulsed evaporation, as well as higher refractive index. The dynamics of film growth during a single laser pulse has been studied by means of a unique thickness monitor.

Optical reflectance technique for observations of submonolayer adsorbed films.

An optical technique is described for detecting and measuring thicknesses of adsorbed films with subangstrom sensitivity. The technique relies on optical interference from an antireflecting thin-film structure that is predeposited on a transparent cell window: the reflectivity of the window depends linearly on the thickness of the molecular layer adsorbed from the gas in the cell.

Reflectometric spectroscopy of adsorbed molecular layers.

A normal-incidence technique is described for obtaining IR absorption spectra of molecular layers adsorbed on a dielectric thin-film surface. In the experiment described, a low-power CO(2) laser beam is scanned across a molecular layer of 2-propanol adsorbed on a ZnSe film. Spectra for 1-5 monolayer coverages are compared with the liquid spectrum of the adsorbate.

Spectral beam combining of a broad-stripe diode laser array in an external cavity.

The outputs from an 11-element, linear diode laser array with broad stripes have been beam combined into a single beam with a beam quality of ~20x diffraction limited in the plane of the junction. This beam combining was achieved by use of a common external cavity containing a grating, which simultaneously forces each array element to operate at a different, but controlled, wavelength and forces the beams from all the elements to overlap and propagate in the same direction. The power in the combined beam was 50% of the output from the bare laser array.