Infrared lasers and optical properties Semiannual report, period ending 31 Oct. 1968

Far infrared laser construction and operation, direct gain measurements, Q switching, and crystal growth of material

Silicon Solar Cell Fabrication Technology

Device fabrication and photoconductive lifetime decay measurements were used to characterize single and polycrystalline silicon substracts. The device characterization of the processed materials was done by spectral response measurements and absolute quantum efficiency at a single wavelength. The results were then reduced to yield the diffusion length of the various samples. The photoconductive lifetime decay method was implemented in order to determine the minority carrier lifetime in unprocessed wafers

Small worlds and board interlocking in Brazil: a longitudinal study of corporate networks, 1997-2007

Social Network Analysis (SNA) is an emerging research field in finance, above all in Brazil. This work is pioneering in that it is supported by reference to different areas of knowledge: social network analysis and corporate governance, for dealing with a similarly emerging topic in finance; interlocking boards, the purpose being to check the validity of the small-world model in the Brazilian capital market, and the existence of associations between the positioning of the firm in the network of corporate relationships and its worth. To do so official data relating to more than 400 companies listed in Brazil between 1997 and 2007 were used. The main results obtained suggest that the configuration of the networks of relationships between board members and companies reflects the small-world model. Furthermore, there seems to be a significant relationship between the firm’s centrality and its worth, described according to an “inverted U” curve, which suggests the existence of optimum values of social prominence in the corporate network

Silicon solar cell fabrication technology

The laser cell scanner was used to characterize a number of solar cells made in various materials. An electron beam-induced current (EBIC) study was performed using a stereoscan scanning electron microscope. Planar p-n junctions were analyzed. A theory for the EBIC based on the analytical solution of the ambipolar diffusion equation under the influence of electron beam excitation parameter z (which is related to beam penetration), the junction depth Z sub j, the beam current and the surface recombination, was formulated and tested. The effect of a grain boundary was studied

Radio-frequency-excited carbon dioxide metal waveguide laser

A new type of waveguide laser is described in which a single-surface concave metal waveguide also doubles as the grounded electrode in a radio-frequency-excited gaseous discharge. The laser’s output modes and spectrum have been studied theoretically and experimentally for cw CO₂ operation of the laser. Overall operating efficiency and mode stability are comparable with those of conventional dielectric waveguide CO₂ lasers, and advantages of the metal waveguide laser include convection cooling, intracavity mode control, and partial self-alignment

Propagation of Airy-Hermite-Gaussian waveguide modes in free space

The cavity modes of metal strip waveguide lasers are most simply expressed in terms of Airy-Hermite-Gaussian functions. The free space propagation of the resulting beam modes has been examined, and both near- and far-field patterns have been calculated and measured. Phase plates may be useful for enhancing the far-field intensity

Emerging materials for solar cell applications: electrodeposited CdTe. First quarter report, February 15-May 15, 1980

The present program is a continuation of earlier efforts to develop electrochemically deposited films of compound semiconductors and solar cells made from them. Primary objectives include the development and characterization of controllably doped n and p type CdTe films with densities of 5.8 gm/cm/sup 3/, appropriate grain sizes, good film morphology and freedom from pinholes, and carrier concentrations from 10/sup 16/ to 10/sup 18//cm/sup 3/. The end result of the effort is to demonstrate by the seventh month, or September 15, 1980, solar cells over 1 cm/sup 2/ in area showing total area conversion efficiencies exceeding 4%. By the end of the first quarter, milestones were met calling for us to supply characterized n type CdTe films that were reproducible and free from pinholes. Also, prototype electrodeposited CdTe solar cells were fabricated and evaluated. Characterizations of p-type CdTe and ZnTe films were complicated by interferences existing between them and adjacent substrates. A number of devices, including the glass/ITO/n-CdTe:In/Au Schottky structure and an ITO/n-CdTe:In/p-Cu/sub 2-x/Te heterojunction, have been fabricated. The highest internal efficiency of the Schottky devices, which have yet to have fingered grids and anti-reflection coatings applied, is 4%. The heterojunction is a larger area device 2 cm/sup 2/ in area. It shows promise of meeting the 4% total area efficiency as does the Schottky when grids and A/R coatings are applied

Emerging materials for solar cell applications: electrodeposited CdTe. Third quarter report, September 1-November 30, 1979

Major emphasis during the period was centered on improving the material properties of electrodeposited CdTe. Using newly devised means for peeling thin CdTe films off the ITO-coated glass substrates, it was possible to accurately measure material density and electrical resistivity. Density proved to be 40% below the bulk CdTe figure of about 6 gm/cm/sup 3/, while resistivity of supposedly doped CdTe films exceeded 10/sup 5/..cap omega.. - cm. These findings prompted initiation of a beneficial change in plating procedures which increased the thin film polycrystalline CdTe density to the bulk value while, at the same time, good columnar growth was obtained. Films made under the old plating process were made into Schottky diodes showing good uniformity and V/sub oc/ values generally exceeding 0.5V. Short circuit current of the best of these was 9.5mA/cm/sup 2/ despite the fact that light entered through a thick gold film and was strongly attenuated

Emerging materials for solar cell applications. First quarter report, February 15-May 31, 1979

Work to develop the theory controlling the electroplating of a compound semiconductor on a transparent, conductive substrate and to demonstrate operative solar cells using the approach is reported. The current program is divided essentially into three paralleled team efforts. The first effort centers on refining the electroplating process at Monosolar so thicker and more uniform layers of p- or n-type cadmium telluride can be plated on both In/sub 2/O/sub 3/:Sn- and Ni- coated substrates. 1 ..mu..M thick polycrystalline films have been achieved for the first time ever without peeling problems, a thickness optimum for maximum solar absorption and economy of materials. Second, work is underway at UCLA to physically and electrically characterize the films and diodes made from them. Under proper conditions Schottky diodes with better than 10/sup 4/ rectification ratios at 1.5 V were obtained along with preliminary indications of grain sizes up to 1 ..mu..M. Measurements of these diodes revealed the presence of deep trapping level(s) that may be associated with plating process impurities that since may have been eliminated. Third, work so far on developing improved techniques for depositing ITO has been successful at UCLA in their effort to eliminate persistent problems with ITO obtained from outside suppliers serving the less demanding liquid crystal display (LCD) industry