Giant Anisotropy of Conductivity in Hydrogenated Nanocrystalline Silicon Thin Films

1998 ◽  
Vol 536 ◽  
Author(s):  
A. B. Pevtsov ◽  
N. A. Feoktistov ◽  
V. G. Golubev

AbstractThin (<1000 Å) hydrogenated nanocrystalline silicon films are widely used in solar cells, light emitting diodes, and spatial light modulators. In this work the conductivity of doped and undoped amorphous-nanocrystalline silicon thin films is studied as a function of film thickness: a giant anisotropy of conductivity is established. The longitudinal conductivity decreases dramatically (by a factor of 109 − 1010) as the layer thickness is reduced from 1500 Å to 200 Å, while the transverse conductivity remains close to that of a doped a- Si:H. The data obtained are interpreted in terms of the percolation theory.

2009 ◽  
Vol 1153 ◽  
Author(s):  
Yuri Vygranenko ◽  
Ehsanollah Fathi ◽  
Andrei Sazonov ◽  
Manuela Vieira ◽  
Gregory Heiler ◽  
...  

AbstractWe report on structural, electronic, and optical properties of boron-doped, hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited by plasma-enhanced chemical vapor deposition (PECVD) at a substrate temperature of 150°C. Film properties were studied as a function of trimethylboron-to-silane ratio and film thickness. The film thickness was varied in the range from 14 to 100 nm. The conductivity of 60 nm thick films reached a peak value of 0.07 S/cm at a doping ratio of 1%. As a result of amorphization of the film structure, which was indicated by Raman spectra measurements, any further increase in doping reduced conductivity. We also observed an abrupt increase in conductivity with increasing film thickness ascribed to a percolation cluster composed of silicon nanocrystallites. The absorption loss of 25% at a wavelength of 400 nm was measured for the films with optimized conductivity deposited on glass and glass/ZnO:Al substrates. A low-leakage, blue-enhanced p-i-n photodiode with an nc-Si p-layer was also fabricated and characterized.


1999 ◽  
Vol 557 ◽  
Author(s):  
T. Toyama ◽  
Y. Kotani ◽  
A. Shimode ◽  
S. Abo ◽  
H. Okamoto

AbstractOptical transitions in nanocrystalline Si (nc-Si) thin films with different mean crystal sizes ranging from < 2 nm to ~3 nm have been studied by electroreflectance (ER) spectroscopy. At 293 K, ER signals are observed at 1.20-1.37 eV to be corresponding to fundamental gap in bulk crystalline Si. With a decrease in the mean crystal sizes of nc-Si, the transition energy of the fundamental gap is increased and the ER signal is intensified. The bandgap widening would be due to quantum confinement (QC) in nc-Si, and the increased signal indicates appearance of direct transition nature. The ER signals are also observed at 2.2 eV and at E1 (E0’) direct gap of 3.1-3.4 eV, while photoluminescence (PL) peak energies are located at 1.65-1.75 eV and at 2.3 eV. With the reduced mean crystal size, the 1.7-eV PL peak energy is also increased, suggesting that QC is also responsible for the increased PL peak energy.


2002 ◽  
Vol 403-404 ◽  
pp. 91-96 ◽  
Author(s):  
C. Gonçalves ◽  
S. Charvet ◽  
A. Zeinert ◽  
M. Clin ◽  
K. Zellama

1997 ◽  
Vol 46 (10) ◽  
pp. 2015
Author(s):  
CHEN GUO ◽  
GUO XIAO-XU ◽  
ZHU MEI-FANG ◽  
SUN JING-LAN ◽  
XU HUAI-ZHE ◽  
...  

2017 ◽  
pp. 97-106
Author(s):  
Atif Mossad Ali ◽  
Takao Inokuma

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