Mikrotechnik für Raumfahrtanwendungen

This contribution describes the preparation, based upon a chemically amplified novolak resist (CAR), electron beam lithography, and ECR plasma etching, of structures with a high aspect ratio (10∶1) and lateral dimensions in the sub-micrometer range (150nm–300nm) which may serve as collector surfaces for sub-μm dust particles in a space experiment.     

High performance analog VLSI computational circuits

Simple linear voltage/current-controlled voltage-to-current (V-T) converters, which are to first-order insensitive to the threshold voltage variation, are introduced. The circuits can be used as basic building blocks to construct simple analog computational circuits, which can perform functions such as square rooting, squaring, multiplication, sum of squares, difference of squares, etc. Some of the key features are: good linearity, floating inputs [high common-mode rejection ratio (CMRR)], simplicity, and good transconductance tuning range. The circuits can be realized with CMOS devices in saturation, however, BiCMOS devices extend their speed and input voltage range. Realistic simulations and experimental results clearly demonstrate the claims     

Distribution of recombination currents in the space charge regionof heterostructure bipolar devices

This paper addresses the problem of the space charge region Shockley-Read-Hall (SRH) recombination currents in heterojunctions with one noncrystalline side. A formulation which generalizes previous works is discussed. The approach is based on the drift-diffusion model with a thermionic-field emission boundary condition. The main physical parameters which determine the relative contribution of each zone of the space charge region (SCR) to the total recombination current are identified. The general analysis is applied for the first time to amorphous/crystalline heterojunctions and design criteria are established to minimize the total recombination current     

Long-wavelength 640×486 GaAs-AlGaAs quantum well infraredphotodetector snap-shot camera

A 9-μm cutoff 640×486 snap-shot quantum well infrared photodetector (QWIP) camera has been demonstrated. The performance of this QWIP camera is reported including indoor and outdoor imaging. The noise equivalent differential temperature (NEΔT) of 36 mK has been achieved at 300 K background with f/2 optics. This is in good agreement with expected focal plane array sensitivity due to the practical limitations on charge handling capacity of the multiplexer, read noise, bias voltage, and operating temperature     

A novel electrochemical process for the production of ammonium perchlorate

Perchloric acid, HCLO₄, and ammonium perchlorate, NH₄ClO₄, of high purity have been produced by electrolysis of chloric acid and subsequent reaction with high purity ammonium hydroxide to produce ammonium perchlorate. The process involves no alkali metals, chlorides or transition metals such as chromates, and thus produces propellant and explosive grade ammonium perchlorate of high purity and with no associated instability or pollution problems. The products can be recovered by solution crystallization-drying or direct spray-drying, respectively.     

Impact and penetration by L/D ≤ 1 projectiles

Calculations of steel target penetration by L/D ≤ 1 tungsten and tungsten alloy projectiles have been extended to L/D = 1/32 over the velocity range 1.5 to 5 km/s. The ratio of crater to projectile diameter tends to 1 as L/D decreases over this entire velocity range. For impact velocities of 1.5 and 3 km/s, penetration depth normalized by projectile length, P/L, increases with decreasing projectile L/D up to a maximum value and then decreases for still lower L/D. Experiments at impact velocities of 2 and 3 km/s confirm these results. For 5 km/s impact velocity, the calculations show P/L increasing with decreasing projectile L/D over the entire range 1/32 ≤ L/D ≤ 1. The projectile L/D for which the maximum P/L occurs appears to depend on the impact velocity. P/L generally scales with impact velocity as P/L v^f(L/D) where f(L/D) ranges from 0 for a long rod to, we believe, 2 in the limit as projectile L/D approaches zero. The calculations show for 1/8 ≤ L/D ≤ 1/2, P/L v^0.9; for L/D = 1/16, P/L v^1.5; and for L/D = 1/32, the new results give P/L v^1.9.