Mixed-phase thin film materials, consisting of nanocrystalline semiconductors embedded within a bulk semiconductor or insulator, have been synthesized in a dual-chamber co-deposition system. A flow-through plasma reactor is employed to generate nanocrystalline particles, that are then injected into a second, capacitively-coupled plasma deposition system in which the surrounding semiconductor or insulating material is deposited. Raman spectroscopy, X-ray diffraction and high resolution TEM confirm the presence of nanocrystals homogenously embedded throughout the a-Si:H matrix. In undoped nc-Si within a-Si:H (a/nc-Si:H), the dark conductivity increases with crystal fraction, with the largest enhancement of several orders of magnitude observed when the nanocrystalline density corresponds to a crystalline fraction of 2-4%. These results are consistent with the nc donating electrons to the surrounding a-Si:H matrix without a corresponding increase in dangling bond density for these films. In contrast, charge transport in n-type doped a/nc-Si:H films is consistent with multi-phonon hopping, possibly through extended nanocrystallite clusters with weak electron-phonon coupling. The flexibility of the dual-chamber co-deposition process is demonstrated by the synthesis of mixed-phase thin films comprised of two distinct chemical species, such as germanium nanocrystallites embedded in a-Si:H and Si nanocrystallites embedded within an insulating a-SiN x:H film.
|Original language||English (US)|
|Title of host publication||Amorphous and Polycrystalline Thin-Film Silicon Science and Technology - 2011|
|Number of pages||12|
|State||Published - 2012|
|Event||2011 MRS Spring Meeting - San Francisco, CA, United States|
Duration: Apr 25 2011 → Apr 29 2011
|Name||Materials Research Society Symposium Proceedings|
|Other||2011 MRS Spring Meeting|
|City||San Francisco, CA|
|Period||4/25/11 → 4/29/11|
Bibliographical noteFunding Information:
The assistance of C. R. Perrey, J. Deneen and C. Barry Carter with high-resolution TEM imaging is gratefully acknowledged, as are insightful conversations with B. I. Shklovskii and P. Stradins. This work was partially supported by NSF grants NER-DMI-0403887, DMR-0705675, IGERT grant DGE-0114372, in part by the MRSEC Program of the NSF-DMR-0212302, NSF grant DMR-0705675, the NINN Characterization Facility, the Xcel Energy grant under RDF contract #RD3-25, NREL Sub-Contract XEA-9-99012-01 and the University of Minnesota.
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