The capacitance of a Schottky barrier diode measured as a function of reverse voltage yields the dope concentration and eventually the thickness of an epitaxially grown silicon layer. It is shown that mercury can be used as the metal contact to the silicon. This allows for a rapid and nondestructive C‒V measurement, particularly when combined with an automated instrument. The results obtained with different surface treatments are discussed. For reliable and reproducible results N‐type silicon should be covered with a thin oxide layer about 50Aå thick, which can easily be made wet chemically. The precision which can be attained with this system in actual practice amounts to ±2% or better and the accuracy depends on the definition of thickness used. This technique with the mercury contacting accessory works equally well on normalGaAs and normalGaP
Co/Pt multilayers with perpendicular anisotropy have recently been shown to be candidate materials for magneto-optic recording.1 In this application the Curie temperature has to be sufficiently low in order to switch the magnetization with the available laser powers. Apart from this technological importance, it is also of fundamental interest to investigate the effect of coupling between two-dimensional systems on their critical behavior. We therefore studied the influence of the Pt thickness on the temperature dependence of the magnetization for Co/Pt multilayers. The multilayers were prepared by vapor deposition in ultrahigh vacuum. X-ray-diffraction measurements confirmed the layered structure. The spontaneous magnetization was obtained by extrapolating the high-field part of the magnetization curves back to zero field. The experiments showed that the changes in the magnetization are reversible up to 450 K. Above 500 K we detected slight irreversible changes probably due to interdiffusion. The Curie temperature decreased with increasing Pt thickness up to about 27 Å, above which no dependence was found. This phenomenon is ascribed to a long-range interaction between the thin (4 or 6 Å) Co layers. The development of a model describing the Curie-temperature dependence on the Pt thickness is in progress. Some preliminary calculations will be given.
For advanced applications of epitaxially grown structures the dope concentration profile and the extent of the concentration gradient between substrate and epitaxial layer are of paramount importance. In order to study these properties with surface probing techniques the interior should be exposed by beveling the slice. The method this paper is focused on, is the spreading resistance technique (1), which is accepted now as a very powerful tool for investigating epitaxially grown structures. Recently also the electroreflectance method was reported (2) to yield promising results when applied to an angle-polished junction. Also the capacitance-voltage (3) and the voltage breakdown methods (4) can be used on beveled structures to profile the junction.Any technique integrates over a certain length and for obtaining a large resolving power in-depth the bevel angle should be as small as possible. This implies, however, that for precise correlation between horizontal position and depth below the original surface the departure from ideal flatness of the slice is taken into account. This note deals with the preparation and evaluation of small bevel angles down to 1/2000. It is concerned with basically known tools and techniques: lapping jigs, polishing procedures, the interference microscope and interferometers. However, in order to fully and correctly exploit the possibilities of the spreading resistance and other methods, on a bevel these techniques should be very critically and carefully applied:The preparation and evaluation procedures are intimately connected. The use of the polishing jig is described in the next section. In semiconductor device technology patterns are optically imaged~ on a slice which therefore should be sufficiently flat. A laseroperated interferometer developed originally to study this surface topography of a silicon slice, is briefly sketched in the third section. Its use in conjunctio~ with the polishing jig for evaluating the local bevel angle, taking into account any departures from perfect flatness of the slice, is explained in the fourth section. It is also shown that by tilting the slice differences in height as low as 60A can be measured. Preparation of the BevelConventional angle-lapping jigs have been used for bevel and stain measurements at relatively large angles by Bond and Smits (5, 12), Fuller and Ditzenberger (6), Gutsche (7), Kane and Larrabee (8), and Herff and Roeder (9). The reliability of these instruments is limited by mechanical tolerances: the play increases with use because it cannot be avoided that powder penetrates between inner and outer cylinders during the lapping process. Moreover, the angle can be measured on the interferometer only before lapping. Here we first describe a more stable and versatile tool, shown schematically in Fig. 1, which matches well the interferometer to be described later.The piston A to which the slice S is attached can slide without play in the holder B and can be fixed at any height and position by screw C. This assembly rests on three balls...
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