scholarly journals Spectroscopic ellipsometry investigation to study the microstructure evolution in boron-doped amorphous silicon films as a result of hydrogen dilution

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Venkanna Kanneboina ◽  
Pratima Agarwal
Keyword(s):  
Dielectric Constant ◽  
Amorphous Silicon ◽  
Microstructure Evolution ◽  
Spectroscopic Ellipsometry ◽  
Peak Position ◽  
Silicon Films ◽  
Angle Of Incidence ◽  
Hydrogen Flow ◽  
Hydrogen Dilution ◽  
Boron Doped

AbstractSpectroscopic ellipsometry (SE) is a sophisticated technique to find the optical constants, bandgap and microstructure of thin layer. SE is used to study the microstructure evolution in boron-doped amorphous silicon films for different hydrogen flow rates (HFR). Spectral dependance of the real and imaginary parts of pseudo-dielectric constant is obtained at a fix angle of incidence (70°). Tauc–Lorentz (T–L) optical model is used to estimate the thickness, bandgap, optical constant and thickness of the top rough layer of the films, whereas Bruggeman effective medium approximation (BEMA) is applied to find the volume fractions of amorphous, crystalline and void phases. A shift in peak position from 3.65 to 4.1 eV in dielectric constant is observed as the hydrogen flow rate is increased from 30 to 70 SCCM. This is accompanied by the emergence of a peak near 3.4 eV, which belongs to the direct bandgap of c-Si. These observations suggest an improvement in microstructure of the films deposited at higher HFR. It is also supported by the observation that films deposited at higher HFR have higher magnitude of amplitude parameter and less broadening. Fitting of experimental data using BEMA also suggests that crystalline fraction increases and amorphous fraction decreases at higher HFR. The bandgap and thickness of top rough layer estimated from SE data are matched well with those obtained using transmission data and atomic force microscopy.

Performances of Nano/Amorphous Silicon Films Produced by Hot Wire Plasma Assisted Technique

1998 ◽  
Vol 507 ◽  
Author(s):  
I. Ferreira ◽  
H. Águas ◽  
L. Mendes ◽  
F. Fernandes ◽  
E. Fortunato ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Transport Properties ◽  
Oxygen Content ◽  
Hydrogen Content ◽  
Crystalline Silicon ◽  
Silicon Films ◽  
Hot Wire ◽  
Hydrogen Dilution ◽  
Nano Crystalline ◽  
Doped Silicon

ABSTRACTThis work reports on the performances of undoped and n doped amorphous/nano-crystalline silicon films grown by hot wire plasma assisted technique. The film's structure (including the presence of several nanoparticles with sizes ranging from 5 nm to 50 nm), the composition (oxygen and hydrogen content) and the transport properties are highly dependent on the filament temperature and on the hydrogen dilution. The undoped films grown under low r.f. power (≍ 4 mWcm−2) and with filament temperatures around 1850 °K have dark conductivities below 10−1Scm−1, optical gaps of about 1.5 eV and photo-sensitivities above 105, (under AM3.5), with almost no traces of oxygen content. N- doped silicon films were also fabricated under the same conditions which attained conductivities of about 10−2Scm−1.

Hydrogen Diffusion in Boron-Doped Hydrogenated Amorphous Silicon Films: Crystallization and Induced Structural Changes

2005 ◽  
Vol 864 ◽  
Author(s):  
F. Kail ◽  
A. Hadjadj ◽  
P. Roca i Cabarrocas
Keyword(s):  
Amorphous Silicon ◽  
Structural Changes ◽  
Hydrogen Diffusion ◽  
Hydrogen Plasma ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Films ◽  
Hydrogen Atoms ◽  
Boron Doped ◽  
Hydrogenated Amorphous ◽  
Positively Charged

AbstractWe have studied the evolution of the structure of boron-doped hydrogenated amorphous silicon films exposed to a hydrogen plasma. From the early stages of exposure, hydrogen diffuses and forms a thick H-rich subsurface. At longer times, hydrogen plasma leads to the formation of a microcrystalline layer via chemical transport without crystallization of the initial layer. We observe that the hydrogen content increases in the films during a plasma exposure and once the microcrystalline layer is formed hydrogen diffuses out of the sample accompanied with a decrease in the boron content. This effect can be attributed to the electric field developed within the heterojunction a-Si:H/μc-Si:H that drives the positively charged hydrogen atoms in the boron-doped layer towards the μc-Si:H layer.

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