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Four pairs of p-i-n structures based on polymorphous Si:H ( pm-Si:H) are fabricated by the method of plasma-enhanced chemical vapor deposition. The structures in each pair are grown on the same substrate so that one of them does not contain Ge in the i-type layer while the other structure contains Ge deposited by molecular-beam epitaxy as a layer with a thickness of 10 nm. The pair differ from one another in terms of the substrate temperature during Ge deposition; these temperatures are 300, 350, 400, and 450°C. The data of electron microscopy show that the structures formed at 300°C contain Ge nanocrystals ( nc-Ge) nucleated at nanocrystalline inclusions at the pm-Si:H surface. The nc-Ge concentration increases as the temperature is raised. The study of the current-voltage characteristics show that the presence of Ge in the i-type layer decreases the density of the short-circuit current in p-i-n structures when they are used as solar cells, whereas these layers give rise to an increase in current at a reverse bias under illumination. The obtained results are consistent with known data for structures with Ge clusters in Si; according to these data, Ge clusters increase the coefficient of light absorption but they also increase the rate of charge-carrier recombination. [ABSTRACT FROM AUTHOR]

The high index of refraction planar optical waveguides operating in the near infrared spectrum were prepared from the intrinsic hydrogenated amorphous silicon (a-Si:H) layer coated by nanocrystalline diamond (NCD). The a-Si:H layers were grown by radio frequency plasma enhanced chemical vapor deposition on glass substrates from silane and hydrogen mixture at the substrate temperature about 250 °C followed at 210 °C by the NCD coating grown by the microwave plasma enhanced chemical vapor deposition from hydrogen rich plasma with adding methane and carbon dioxide at the substrate temperature. The optical absorptance spectra, Raman spectra and scanning electron microscopy reveal the diamond character of the NCD coatings as well as the stability of a-Si:H layer during NCD deposition. The critical issue of the NCD coated a-Si:H optical waveguide is the optical absorption in NCD coating. The Finite Element Method simulations show that the near infrared optical absorption coefficient of the NCD coating must be reduced below 10/cm to reduce the optical attenuation below 1 dB/cm in the planar waveguide with the 50 nm thick NCD coating. [ABSTRACT FROM AUTHOR]

Abstract: It is important for optical applications of nanocrystalline diamond to achieve low optical absorption as well as optical scattering. We discuss the optical and photocurrent spectra measured by the transmittance and reflectance, photothermal deflection spectroscopy, laser calorimetry and dual beam photocurrent spectroscopy of low non-diamond content nanocrystalline diamond films grown by microwave plasma enhanced chemical vapor deposition on fused silica glass substrates. [Copyright &y& Elsevier]

Abstract: We present photocurrent spectra of nominally undoped nanocrystalline diamond (NCD) films grown on glass substrates by hot filament (HF) and microwave (MW) plasma enhanced chemical vapor deposition (CVD). The spectra were measured in a broad optical range (200–2000 nm) by dual-beam photocurrent spectroscopy (DBP) and Fourier-transform photocurrent spectroscopy (FTPS) in amplitude modulated step scan mode. The NCD films with carefully oxidized surface show photosensitivity and high dark resistivity. Unlike single crystal type IIa diamond with the photonization threshold at 5.5 eV, the photocurrent spectra of NCD films are dominated by the “non-diamond phase” with the photo-ionization threshold at about 0.8 eV. Some HF CVD samples have lower sub-band gap absorption (non-diamond phase contamination). The non-diamond phase content increases after annealing at elevated temperature. The non-diamond phase content can be reduced by exposing NCD to hydrogen plasma at temperature below 350 °C. [Copyright &y& Elsevier]

Abstract: In this paper we report the results of a study assessing a newly developed deposition process for F-doped SnO2 films by CVD operating at atmospheric pressure (APCVD). The technology is designed to be compatible with industrial requirements such as high process speed, possible up-scaling to wide substrate widths and low costs. The optical and electrical properties of layers deposited on glass are found to be similar to those of commercially available low pressure CVD. Optical absorptance below 1% is achieved for films of around 0.8μm thick. Such transparent conductive oxide (TCO) is used with a-Si:H single junction p–i–n solar cells grown by PECVD. The cells are characterised by I–V measurements using AM1.5 spectra and by measuring the external quantum efficiencies (EQE). The initial efficiencies were up to 9.3% with FF=73%. The TCO films demonstrated an enhanced performance in the EQE compared to commercially available TCO (Asahi-U). [Copyright &y& Elsevier]