Juraić, Krunoslav
(2012)
Amorphous-nanocrystalline silicon thin films: structural and optical properties.
Doctoral thesis, University of Zagreb, Faculty of Science.
Abstract
Structural and optical properties of amorphous-nanocrystalline silicon thin films, 100-400 nm
thick, prepared by plasma-enhanced chemical-vapor deposition using silane and hydrogen
mixture were investigated. By using increased discharge power (100-180 W/m2) and highly
diluted mixture of silane and hydrogen (94-95% hydrogen), nanocrystalline silicon thin films
with crystallinity from completely amorphous up to 38% percent and wide log-normal size
distribution of nanocrystals with average size 2-9 nm were obtained. Thin film growth
appears to be governed both by deposition and plasma etching forming completely amorphous
layer in the beginning stages of deposition. During the etching process ordered centers for
nanocrystals formation are formed. In that way the samples are completely amorphous close
to substrate, and the crystallinity and size of nanocrystals are larger close to the surface.
Defects density (mainly dangling bonds that are mostly concentrated at grain boundaries)
increased with the volume contribution of nanocrystals. Optical properties (absorption
coefficient and optical band gap) are highly correlated to the size and crystallinity of
nanocrystals. That is result of quantum size effect. By varying size and volume fraction of
silicon nanocrystals incorporated in amorphous matrix it were obtained samples with
increased optical bandgap from 1.7 eV (value characteristic for a-Si:H) up to 2.1 eV for the
most crystalline sample. Those samples are incorporated in p-i-n structure of thin film solar cells. It results in the blue shift of up to 20 nm in the quantum efficiency maximum, compared
to the value characteristic for completely amorphous silicon.
| Item Type: |
Thesis
(Doctoral thesis)
|
| Uncontrolled Keywords: |
amorphous-nanocrystalline silicon; nanocrystals; thin films; HRTEM; Raman;
GIXRD; GISAXS; PDS; optical properties; structural properties; solar cell
quantum efficiency |
| Subjects: |
NATURAL SCIENCES > Physics > Condensed Matter Physics |
| Divisions: |
Division of Materials Physics |
| Projects: |
| Project title | Project leader | Project code | Project type |
|---|
| Tanki filmovi legura silicija na prijelazu iz amorfne u uređenu strukturu | [82826] Davor Gracin | 098-0982886-2894 | MZOS |
|
| Depositing User: |
Krunoslav Juraić
|
| Date Deposited: |
10 Jun 2013 18:27 |
| URI: |
http://fulir.irb.hr/id/eprint/555 |
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