Buckled SiGe films on viscous oxide with different Ge content are studied by wafer bonding and smart-cut process. Compressively strained SiGe layers on the viscous oxide were relaxed to form the buckled state after thermal treatment. Two-dimensional buckling on blanket films is observed. A higher Ge concentration results in a smaller buckling amplitude and a smaller buckling period. Both buckling amplitude and period increase as oxidation time is increased. A small SiGe film ͑mesa͒ area can inhibit buckling. Semiempirical analysis gives the critical area size, below which no buckling is observed in the equilibrium states. The critical area size decreases with increasing Ge concentration and decreasing thickness of SiGe films.
The Ge-on-insulator metal-oxide-semiconductor detector was fabricated by the wafer bonding and smart-cut. The surface roughness after smart-cut is reduced to be ~7 nm at 150ºC, due to the suppression of hydrogen outdiffusion. The large work function metal (Pt) is used for the gate electrode on the n- type Ge on insulator to reduce the dark current. Due to the small bandgap of Ge, the 850 nm, 1.3 μm and 1.55 μm infrared can be detected. The increasing photo response of the detector using the Ge-on-insulator with decreasing bonding temperature also indicates that the defects caused by hydrogen implantation are passivated more effectively by hydrogen at lower temperature. In order to increase the responsivity of 1.3 μm infrared, n-Ge thickness of 1.3 μm is used, and the responsivity reaches 231 mA/W. The external mechanical strain can further enhance the photo current without degradation of dark current.
This paper is to present the design and development of a piezoelectric actuator for SPM in ultrahigh vacuum (10−7∼10−9 Torr). The measuring probe is installed on a precise scanning actuator, which is further driven by a fast approaching actuator. The precise scanning actuator composed of a piezo-tube with segmented electrodes can realize 3-D precise scanning motions at subnanometer level to move the measuring probe over the measured surface. Because of its stable and smooth actuating behavior, the inchworm actuating principle is selected for the fast approaching actuator, which is build up with two controllable clamping devices and an actuating device. Diverse flexure mechanisms are applied in the actuator to attain frictionless guiding and recovery functions. To realize balanced clamping forces on the scanning tube, each clamping device is integrated with a fine regulating mechanism for clamping force. By applying the theoretical model and the finite element analysis, the relations between force and deflection inside the actuator were investigated to validate its function. The developed actuator has sustained the severe baking and pumping process, and their function and performance were verified experimentally in ultrahigh vacuum.
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