Abstract
A dual-plasma codeposition system capable of synthesizing thin films of mixed-phase materials consisting of nanoparticles of one type of material embedded within a thin film semiconductor or insulator matrix is described. This codeposition process is illustrated by the growth of hydrogenated amorphous silicon (a-Si:H) films containing silicon nanocrystalline inclusions (a/nc-Si:H). A capacitively coupled flow-through plasma reactor is used to generate silicon nanocrystallites of diameter 5 nm, which are entrained by a carrier gas and introduced into a capacitively coupled plasma enhanced chemical vapor deposition reactor with parallel plate electrodes, in which a-Si:H is synthesized. The structural and electronic properties of these mixed-phase a/nc-Si:H films are investigated as a function of the silicon nanocrystal concentration. At a moderate concentration (crystalline fraction 0.02-0.04) of silicon nanocrystallites, the dark conductivity is enhanced by up to several orders of magnitude compared to mixed-phase films with either lower or higher densities of nanoparticle inclusions. These results are interpreted in terms of a model whereby in films with a low nanocrystal concentration, conduction is influenced by charges donated into the a-Si:H film by the inclusions, while at high nanocrystal densities electronic transport is affected by increased disorder introduced by the nanoparticles.
| Original language | English (US) |
|---|---|
| Article number | 043704 |
| Journal | Journal of Applied Physics |
| Volume | 107 |
| Issue number | 4 |
| DOIs | |
| State | Published - 2010 |
Bibliographical note
Funding Information:This work was partially supported by the NSF under Grant Nos. NER-DMI-0403887 and DMR-0705675, the NINN Characterization Facility, the Xcel Energy grant under RDF Contract No. RD3-25, and the University of Minnesota Center of Nanostructure Applications. Lee Wienkes’ assistance with optical absorption measurements and helpful comments from Paul Stradins and C. Blackwell are gratefully acknowledged. Y.A. and C.A. contributed equally to this work.
