Signature of growth-deposition technique on the properties of PECVD and thermal SiO2

In this article, we report the process induced variation in the characteristics of PECVD deposited and thermally grown silicon dioxide (SiO2) thin film. We find key differences in the porosity, arrangement of the nano-pores, surface roughness, refractive index and electrical resistivity of the SiO2 thin films obtained by the two methods. While the occurrence of the nanoporous structure is an inherent property of the material and independent of the process of film growth or deposition, the arrangements of these nano-pores in the oxide film is process dependent. The distinct arrangements of the nano-pores are signatures of the deposition/growth processes. Morphological analysis has been carried out to demonstrate the difference between oxides either grown by thermal oxidation or through PECVD deposition. The tunable conductive behavior of the metal filled nano-porous oxides is also demonstrated, which has potential to be used as conductive oxides in various applications

Fabrication and Optical Properties of a Fully Hybrid Epitaxial ZnO-Based Microcavity in the Strong Coupling Regime

In order to achieve polariton lasing at room temperature, a new fabrication methodology for planar microcavities is proposed: a ZnO-based microcavity in which the active region is epitaxially grown on an AlGaN/AlN/Si substrate and in which two dielectric mirrors are used. This approach allows as to simultaneously obtain a high-quality active layer together with a high photonic confinement as demonstrated through macro-, and micro-photoluminescence ({\mu}-PL) and reflectivity experiments. A quality factor of 675 and a maximum PL emission at k=0 are evidenced thanks to {\mu}-PL, revealing an efficient polaritonic relaxation even at low excitation power.Comment: 12 pages, 3 figure

Photoluminescence of nc-Si:Er thin films obtained by physical and chemical vapour deposition techniques: The effects os microstructure and chemical composition

Erbium doped nanocrystalline silicon (nc-Si:Er) thin films were produced by reactive magnetron rf sputtering and by Er ion implantation into chemical vapor deposited Si films. The structure and chemical composition of films obtained by the two approaches were studied by micro-Raman scattering, spectroscopic ellipsometry and Rutherford backscattering techniques. Variation of deposition parameters was used to deposit films with different crystalline fraction and crystallite size. Photoluminescence measurements revealed a correlation between film microstructure and the Er3+ photoluminescence efficiency.FCT Project POCTI/CTM/39395/2001INTAS Project #03-51-648

Electronic and structural properties of doped amorphous and nanocrystalline silicon deposited at low substrate temperatures by radio-frequency plasma-enhanced chemical vapor deposition

The gas phase doping of hydrogenated amorphous silicon and hydrogenated nanocrystalline silicon thin films deposited on glass and on plastic (polyethylene terephthalate) substrates is reported. Two substrate temperatures were used during deposition: 25 degreesC and 100 degreesC. Films were deposited by radio-frequency plasma-enhanced chemical vapor deposition using phosphine or diborane for n- or p-type doping, respectively. Similar electronic and structural properties are obtained for the doped films deposited on either substrate. Hydrogen dilution of silane is used to improve the electronic and structural properties of the amorphous films and to obtain nanocrystalline films. The most conductive amorphous films have n-type dark conductivity at room temperature similar to10(-3) Omega(-1) cm(-1) and similar to10(-5) Omega(-1) cm(-1) when deposited at 100degreesC and 25degreesC, respectively, or p-type room-temperature dark conductivity similar to10(-7) Omega(-1) cm(-1) at both substrate temperatures. The most conductive nanocrystalline films deposited at 100 degreesC have n- and p-type dark conductivity at room temperature above 10(-2) Omega(-1) cm(-1) while nanocrystalline films deposited at 25 degreesC only have p-type conductivity higher than 10(-2) Omega(-1) cm(-1) at room temperature. Isochronal annealing at temperatures up to 300 degreesC showed that the dopants are fully activated at the deposition temperature in doped nanocrystalline samples and that they are only partially activated in amorphous films deposited at low substrate temperatures.Fundação para a Ciência e Tecnologia (FCT) Universidade do Minho (UM

Deposition of silicon nitride thin films by hot-wire CVD at 100ºC and 250ºC

Silicon nitride thin films for use as passivation layers in solar cells and organic electronics or as gate dielectrics in thin-film transistors were deposited by the Hot-wire chemical vapor deposition technique at a high deposition rate (1-3 Ǻ/s) and at low substrate temperature. Films were deposited using NH3/SiH4 flow rate ratios between 1 and 70 and substrate temperatures of 100º C and 250ºC. For NH3/SiH4 ratios between 40 and 70, highly transparent (T ~ 90%), dense films (2.56 - 2.74 g/cm3) with good dielectric properties and refractive index between 1.93 and 2.08 were deposited on glass substrates. Etch rates in BHF of 2.7 Ǻ/s and 10 MV cm−1.Fundação para a Ciência e Tecnologia (FCT) - FCT/CNRS programa com o contracto no. 20798, bolsa de investigaçao e projecto PTDC-CTM-66558-200

Piezoresistor sensor fabrication by direct laser writing on hydrogenated amorphous silicon

In this paper we report on the 532 nm Nd:YAG laser-induced crystallization of 10 nm thick boron-doped hydrogenated amorphous silicon thin films deposited on flexible polyimide and on rigid oxidized silicon wafers by hot-wire chemical vapor deposition. The dark conductivity increased from ~10-7 -1cm-1, in the as-deposited films, to ~10 and 50 -1cm-1 after laser irradiation, on rigid and flexible substrates, respectively. Depending on type of substrate, laser power and fluence, a Raman crystalline fraction between 55 and 90% was measured in HWCVD films, which was higher than observed in rf-PECVD films (35 - 55%). Crystallite size remained small in all cases, in the range 6-8 nm. Due to a very high conductivity contrast (>7 orders of magnitude) between amorphous and crystallized regions, it was possible to define conductive paths in the a-Si:H matrix, by mounting the sample on a X-Y software-controlled movable stage under the laser beam, with no need for the usual lithography steps. The resistors scribed by direct laser writing had piezoresistive properties, with positive gauge factor ~1. The details of the laser interaction process with the Si film were revealed by scanning electron microscopy imaging.(undefined

High-rate deposition of nano-crystalline silicon thin films on plastics

Nanocrystalline silicon (nc-Si:H) is commonly used in the bottom cell of tandem solar cells. With an indirect bandgap, nc-Si:H requires thicker (∼1 µm) films for efficient light harvesting than amorphous Si (a-Si:H) does. Therefore, thin-film high deposition rates are crucial for further cost reduction of highly efficient a–Si:H based photovoltaic technology. Plastic substrates allow for further cost reduction by enabling roll-to-roll inline deposition. In this work, high nc-Si:H deposition rates on plastic were achieved at low substrate temperature (150 °C) by standard Radio-frequency (13.56 MHz) Plasma Enhanced Chemical Vapor Deposition. Focus was on the influence of deposition pressure, inter-electrode distance (1.2 cm) and high power coupled to the plasma, on the hydrogen-to-silane dilution ratios (HD) necessary to achieve the amorphous-to-nanocrystalline phase transition and on the resulting film deposition rate. For each pressure and rf-power, there is a value of HD for which the films start to exhibit a certain amount of crystalline fraction. For constant rf-power, this value increases with pressure. Within the parameter range studied the deposition rate was highest (0.38 nm/s) for nc-Si:H films deposited at 6 Torr, 700 mW/cm2 using HD of 98.5 %. Decreasing the pressure to 3 Torr (1.5 Torr) and rf-power to 350 mW/cm2 using HD – 98.5 % deposition rate is 0.12 nm/s (0.076 nm/s). Raman crystalline fraction of these films is 72, 62 and 53 % for the 6, 3 and 1.5 Torr films, respectively.Fundação para a Ciência e a Tecnologia (FCT)DREBM/PICS_CNRS/201