The role of ions on the growth of microcrystalline silicon films produced by the standard hydrogen dilution of silane in a radio frequency glow discharge is studied through the analysis of the structural properties of thick and thin films. Spectroscopic ellipsometry is shown to be a powerful technique to probe their in-depth structure. It allows to evidence a complex morphology consisting of an interface layer, a bulk layer, and a subsurface layer. The ion energy has been tuned by codepositing series of samples on the grounded electrode and on the powered electrode, as functions of pressure and power. On the one hand, reducing the ion energy through the increase of the total pressure and depositing on the grounded electrode, favors the formation of large grains and results in improved bulk transport properties, but leaves an amorphous interface layer with the substrate. On the other hand, we achieve fully crystallized films on glass substrates under conditions of high energy ion bombardment. We suggest that ion bombardment, and particularly the implantation of hydrogen ions, favors the formation of a porous layer where the nucleation of crystallites takes place. These results are further supported by in situ spectroscopic ellipsometry measurements of the film morphology as a function of the ion energy.

No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

International audienceMicrocrystalline siliconthin films prepared by the layer-by-layer technique in a standard radio-frequency glow discharge reactor were used as the active layer of top-gate thin-film transistors(TFTs). Crystalline fractions above 90% were achieved for silicon films as thin as 40 nm and resulted in TFTs with smaller threshold voltages than amorphous siliconTFTs, but similar field effect mobilities of around 0.6 cm2/V s. The most striking property of these microcrystalline silicontransistors was their high electrical stability when submitted to bias-stress tests. We suggest that the excellent stability of these TFTs, prepared in a conventional plasma reactor, is due to the stability of the μc-Si:H films. These TFTs can be used in applications that require high stability for which a-Si:HTFTs cannot be used, such as multiplexed row and column drivers in flat-panel display applications, and active matrix addressing of polymer light-emitting diodes