Using thin film stress to produce precision, figured x-ray optics

84. Chih-Chung Chou; Gregory, D. A. Three-dimensional nanometer structures. Microwave and Optical Technology Letters. 1993 Apr; Three-dimensional (3D) structures in the nanometer range are difficult to create by conventional planar approaches. Having this capability would extend the variety of nanodevices, increase the device unit volume density dramatically, and approach a more completely miniaturized and integrated version of practical device systems. Such systems would be an advantage in signal processing because of low energy consumption and improved measurement resolution. 85. Fotino, M. Tip sharpening by normal and reverse electrochemical etching. Review of Scientific Instruments. 1993 Jan; The author's work deals with the characteristics and formation by electrochemical etching under AC voltage of very sharp metal tips usable in several applications and in particular in scanning probe microscopy (scanning tunneling microscopy (STM) and atomic force microscopy). An exhaustive survey of other existing mechanical and physicochemical procedures for producing sharp tips is also included for background comparison. Because tip sharpness is central to the atomic or nearatomic resolution attainable by STM, yet appears to be so far incompletely studied or documented in the literature, it is argued that high-resolution evidence is required for proper tip characterization as a prerequisite toward adequate performance in the nanometer range. Although atomic-resolution imaging of two-dimensional (flat) surfaces by STM has been possible with tips of ill defined or large apex radii, comparable performance on three-dimensional (rough) surfaces requires the use of tips with sleek shanks and apex radii smaller than or at least commensurate with the desired resolution. The central role played in electrochemical etching under AC voltage by bubble dynamics in shaping the tip apex is analyzed. Experimental results embodied in high-magnification micrographs obtained by high-resolution transmission electron microscopy are presented to illustrate both the intrinsic limitation imposed by large apex radii usually obtained by electrochemical etching in normal configuration (tip oriented downward) and the greatly enhanced sharpening action of the reverse configuration (tip oriented upward) that produces ultrasharp tips of nanometer and subnanometer apex dimensions (nanotips). 86. Syoji, Katuo; Kuriyagawa, Tunemoto; Zhou, Libo; Suzuki, Hidetoshi; Aihara, Hideo. Truing of super-abrasive wheels for form-grinding. Journal of the Japan Society of Precision Engineering. 1993 Mar; 59(3): 485-490. Diamond or CBN wheels are widely used now, but the application of these wheels in form-grinding is still limited due to the difficulty of truing. The subject of study is to achieve the technology of truing super-abrasive wheels for the form-grinding. In the present paper, a new technique using a cup-type GC wheel is proposed, and the truing device is designed and produced. This device can true a wheel into any convex shape, through envelope of lines made by the cup-type GC truer. The fundamental characteristics including truing efficiency and accuracy are also investigated by truing a CBN grinding wheel. The excellent truing performance of this device is demonstrated by grinding following truing. 6 Refs. 87. Suga, T. Ultraprecision machining. Journal of the Japan Society of Mechanical Engineers. 1992 Oct. 5; 95(887) It is said that the image of ultraprecision improved from 0.1 I~m to 0.01 ~m within recent years. Ultraprecision machining is a production technology which forms what is called nanotechnology with ultraprecision measuring and ultraprecision control. Accuracy means average machined sizes close to a required value, namely the deflection errors are small; precision means the scattered errors of machined sizes agree very closely. The errors of machining are related to both of the above errors and ultraprecision means the combined errors are very small. In the present ultraprecision machining, the relative precision to the size of a machined object is said to be in the order of 10"6. The flatness of silicon wafers is usually < 0.5 I~m. It is the fact that the appearance of atomic scale machining is awaited as the limit of ultraprecision machining. The machining of removing and adding atomic units using scanning probe microscopes are expected to reach the limit actually. 2 Refs. 88. Drexler, K. Eric; Peterson, Chris; Pergamit, Gayle. Unbounding the Future: The Nanotechnology Revolution. Morrow; 1993 Jul. ISBN 0-688-12573-5. $11.50. 89. Yuan, F; Shi, Y; Knight, L. V; Perkins, R. T; AIIred, D. D. Using thin film stress to produce precision, figured x-ray optics. Thin Solid Films. Nov. 20; 220(1-2): 284-288. We are studying the possibility of producing precision, aspherical mirrors for X-rays and visible light. Our study examines the use of ultrastructure processing to replace mechanical methods of matedal removal. The method starts with a chemically-mechanically polished, flat silicon wafer. The aim is to preserve atomic scale smoothness of the surface wafer while the wafer is bent to a desired figure. We report measurements of the mechanical properties of various stressing layers. This involves measuring the deformation of several thin silicon wafers coated with chemically vapor deposited nickel and boron films of known thickness. We have found that, under normal conditions, the film does not add to the microroughness of the substrata on either the front or the back surfaces. Film and substrata thicknesses, however, vary by as much as 10%. This is the present limit on figure accuracy. We have developed a model that describes bending of B/Si and Ni/Si structures. The model relates stress and Young's modulus to the measured thickness of the film, and the thickness and curvature of the substrate. This approach is used to measure the stress and Young's modulus for boron and nickel films. The Young's modulus Ef was 3.05 x 1012 Pa for the boron films and 1o4 x 1010 Pa for the nickel films. From the relationship developed and verified for predicting the radii of curvature of the substrate, it may be possible to define a film thickness pattem which would provide a desired optical figure. 8 Refs. 90. Yoshioka, Masato. Wave form of grinding force for single grain grinding - Grinding of a brittle material by a single abrasive grain (2nd report). Journal of the Japan Society of Precision Engineering. 1993 Mar; 59(3): 515520. In this study, several kinds of materials are circularly ground with a diamond cone indenter and the wave form of grinding force is recorded. It can be expected that the wave form reflects the difference of grinding mechanism among various grinding conditions or the kinds of materials. The vertical component of grinding force differs markedly from the horizontal component in its wave form. That is, the former reaches maximum rapidly after the beginning of grinding, while the latter only gradually increases and becomes maximum around the deepest grinding point. The difference in the wave form is thought to be due to the following two causes: (1) slipping of the indenter tip on the ground surface, (2) strain rate dependence of gdnding force. 306

OCTOBER 1993 VOL 15 NO 4