One of the critical components in a thermophotovoltaic (TPV) system is the infrared-sensitive photovoltaic (PV) semiconductor device that converts the emitted radiation to electricity. Currently, several semiconductor material systems are under development by various workers in the field. The most common are InGaAs/InP, GaSb, and InGaSbAs/GaSb. These devices normally have electronic energy bandgap values in the range of 0.50–0.74 eV. In addition, the design and structure of these devices fall into two distinct formats: conventional planar and monolithic interconnected module (MIM). The conventional planar devices normally have one semiconductor junction and are high-current/low-voltage devices. In a MIM, small area PV cells are connected in series monolithically, on a semi-insulating substrate. This results in the formation of a single high-voltage/low-current module. Electrical and optical performance results for MIMs with electronic energy bandgaps of 0.60 and 0.74 eV will be presented.

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) cells series-connected on a single semi-insulating indium phosphide (InP) substrate. The MIM is exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies.Initial MIM development has focused on a 1 cm(2) device consisting of eight series interconnected cells. MIM devices, produced from 0.74 eV InGaAs, have demonstrated V-oc=3.2 V, J(sc)=70 mA/cm(2) and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurements (>2 mu m) of these devices indicate a reflectivity of >82%. MIM devices produced from 0.55 eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

A series of metals was examined for suitability for the Wheel Abrasion Experiment, one of ten microrover experiments of the Mars Pathfinder Mission. The seven candidate metals were: Ag, Al, Au, Cu, Ni, Pt, and W. Thin films of candidate metals from 0.1 to 1.0 micrometer thick were deposited on black anodized aluminum coupons by e-beam and resistive evaporation and chemical vapor deposition. Optical, corrosion, abrasion, and adhesion criteria were used to select Al, Ni, and Pt. A description is given of the deposition and testing of thin films, followed by a presentation of experimental data and a brief discussion of follow-on testing and flight qualification.

Wild turkey sex and age information is needed to define population structure but is difficult to obtain. We classified age and gender of Merriam’s turkeys (Meleagris gallopavo merriami) accurately based on measurements of two foot characteristics. Gender of birds was correctly classified 93% of the time from measurements of middle toe pads; correct classification of age and gender combined decreased to 78%. Measurements from the middle toenail to heel pad correctly classified gender 98% of the time; correct classification of age and gender of birds was 94%. An independent test of this technique on Merriam’s turkeys from Colorado using measurements of the middle toe pads correctly classified the gender of Merriam’s 99% of the time; gender and age combined were correctly classified only 50% of the time.

Hydrogenated and nonhydrogenated nitrogen containing diamondlike carbon films (NDLC including a-C:N and a-C:N:H) were made in a dual ion beam deposition system. The asdeposited films were characterized by Raman spectroscopy, Rutherford backscattering spectroscopy (RBS) and elastic recoil detection analysis (ERD). The compositional stability of the films at temperatures up to 550°C was examined in situ by both RBS and ERD using a heated sample stage in the scattering chamber. The addition of nitrogen altered the Raman parameters when compared with conventional DLC. At elevated temperatures, the a-C:N films do not suffer nitrogen loss; however, the a-C:N:H films undergo nitrogen and hydrogen loss at 400°C.

A wide variety of energetically assisted methods have been employed to grow diamond films at low pressures. Common features of the processes include the presence of atomic hydrogen, energetic carbon containing fragments and high surface mobilities. Some understanding of the molecular processes taking place during nucleation and growth of diamond has been achieved, but detailed molecular mechanisms are not known with certainty. Application of vapor grown diamond for abrasive grit, tool coatings and wear resistant surfaces can be expected shortly. However, the use of vapor grown, crystalline diamond in optical applications or as active semiconductor elements will require further control over surface roughness and crystalline quality. Related research has led to the discovery of a new class of materials, the so-called "diamondlike" phases. Two types of diamondlike materials may be distinguished, namely, the diamondlike hydrocarbons and the diamondlike carbons. These materials possess exceptional hardness, smoothness and chemical inertness. They show promise as combined anti-reflection and abrasion resistant coatings on optical elements, as protective coatings on magnetic and optical disks, as diffusion barriers and for photo-lithographic applications.

A major factor limiting the efficiency of the GaAs-GaAlAs solar cell is the rate of recombination at the GaAs-AlGaAs interface. Evidence has been previously reported which indicates that recombination at this interface can be greatly reduced if the AlGaAs layer is grown at lower than normal temperatures. The authors examine the epitaxial growth of AlGaAs on GaAs using a horizontal OMCVD reactor and an excimer laser operating in the UV (lambda = 193 nm) region. The growth temperatures were 450 and 500 C. The laser beam was utilized in two orientations: 75 deg angle of incidence and parallel to the substrate. Film composition and structure were determined by Auger electron spectroscopy (AES) and transmission electron microscopy (TEM). Auger analysis of epilayers grown at 500 C with the laser impinging show no carbon or oxygen contamination of the epitaxial layers or interfaces. TEM diffraction patterns of these same epilayers exhibit single crystal (100) zone axis patterns.

Forty wild-trapped white-tailed ptarmigan (Lagopus leucurus) were released onto Pike's Peak, Colorado, in June (six mated pairs) and September (9 males, 7 females, 12 juveniles) 1975. Numbers declined 37.5% by the first spring (1976) after the introduction. Spring densities gradually recovered, increasing from 3.4 grouse per 100 ha of breeding habitat in 1976 to 8.4 in 1979, then declined to 7.4 in 1980. Mean distance of territories from the release area increased only 0.86 km (p = 0.44) from 1976 to 1980, reflecting a slow process of expansion. Reproduction was documented in all years including 1975. Survival of released birds until 1976 was 93.3% for males, 46.1% for females, and 33.3% for juveniles. Time of release did not influence survival. Average annual survival (1976–1980) was 64.9% for adult males, 60.3% for adult females, and 43.1% for juveniles. Yearlings comprised 39.7% (range, 20.0 to 54.9%) of all birds (N = 219) identified exclusive of juveniles. Of the 219 birds identified, 137 (62.6%) were males.