scholarly journals Effect of Silicon Crystal Size on Photoluminescence Appearance in Porous Silicon

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Pushpendra Kumar
Keyword(s):  
Porous Silicon ◽  
Crystal Size ◽  
Energy Gap ◽  
Electrochemical Etching ◽  
Silicon Crystal ◽  
Nanocrystalline Silicon ◽  
Different Temperatures ◽  
Nano Crystal ◽  
Optical Silicon

The photoluminescence (PL) study in porous silicon (PS) with decreasing Si crystallites size among the pores was reported. The PL appearance is attributed to electronic confinement in columnar-like (or dotlike) structures of porous silicon. Three different pore diameter PS samples were prepared by electrochemical etching in HF-based solutions. Changes in porous silicon and Si crystallite size were studied by observing an asymmetric broadening and shift of the optical silicon phonons in Raman scattering. Fourier transform infrared spectroscopy (FTIR) was used to study the role of siloxene or other molecular species, for example, in the luminescence mechanism. This mechanism was further studied by thermal annealing of PS at different temperatures. The PL of PS sample annealed at ≥300°C for 1 hr shows that trap electronic states appear in the energy gap of the smaller nano-crystal when Si–O–Si bonds are formed. From the observation of PL, Raman, and FTIR spectroscopy, the origin of PL in terms of intrinsic and extrinsic properties of nanocrystalline silicon was discussed.

Deposition of Photoluminescent Nanocrystalline Silicon Films by SiF4-SiH4-H2 Plasmas

1996 ◽  
Vol 452 ◽  
Author(s):  
G. Cicala ◽  
G. Bruno ◽  
P. Capezzuto ◽  
L. Schiavulli ◽  
V. Capozzi ◽  
...  
Keyword(s):  
Grain Size ◽  
Porous Silicon ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Energy Gap ◽  
Chemical Vapor ◽  
Nanocrystalline Silicon ◽  
X Ray Diffraction ◽  
X Ray ◽  
Average Grain Size

AbstractVisible photoluminescence at 1.62 eV has been observed at room temperature from fluorinated and hydrogenated nanocrystalline silicon (nc-Si:H,F) produced in a typical plasma enhanced chemical vapor deposition system. The use of SiF4-SiH4-H2 mixture, because of the H2 dilution and the presence of SiF4, favours the amorphous - crystalline transition through the etching process of the amorphous phase. The x - ray diffraction measurements give an average grain size of about 100 Å. The presence of these nanocrystals shifts the absorption edge of the films towards higher energy. An energy gap of 2.12 eV is estimated, although the hydrogen content in the material is only 4.5 at. %. The temperature dependence of the photoluminescence behaves similarly to that of porous silicon.

scholarly journals The Effect of Etching Time On Structural Properties of Porous Quaternary AlInGaN Thin Films

2021 ◽  
Vol 19 (50) ◽  
pp. 77-83
Author(s):  
Ghasaq Ali Tomaa ◽  
Alaa Jabbar Ghazai
Keyword(s):  
Porous Silicon ◽  
Crystal Size ◽  
Electrochemical Etching ◽  
Silicon Layer ◽  
Porous Silicon Layer ◽  
Etching Time ◽  
Etching Technique ◽  
Force Microscopy ◽  
Atomic Force ◽  
Homogeneous Pattern

Using photo electrochemical etching technique (PEC), porous silicon (PS) layers were produced on n-type silicon (Si) wafers to generate porous silicon for n-type with an orientation of (111) The results of etching time were investigated at: (5,10,15 min). X-ray diffraction experiments revealed differences between the surface of the sample sheet and the synthesized porous silicon. The largest crystal size is (30 nm) and the lowest crystal size is (28.6 nm) The analysis of Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscope (FESEM) were used to research the morphology of porous silicon layer. As etching time increased, AFM findings showed that root mean square (RMS) of roughness and porous silicon grain size decreased and FESEM showed a homogeneous pattern and verified the formation of uniform porous silicon.

scholarly journals Low-Temperature Co-Precipitation Synthesis of HoFeO3 Nanoparticles

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 238
Author(s):  
Vo Quang Mai ◽  
Nguyen Anh Tien
Keyword(s):  
Low Temperature ◽  
Single Phase ◽  
Crystal Size ◽  
Energy Gap ◽  
Precipitation Method ◽  
Optical Energy Gap ◽  
Superparamagnetic Behaviour ◽  
Different Temperatures ◽  
Co Precipitation ◽  
20 Nm

In this research, we investigate and discuss the characteristics of HoFeO3 nanoparticles synthesized by the co-precipitation method at low temperature (t° ≤ 4 °C). The single-phase HoFeO3 samples with the orthorhombic structure formed after annealing of the precipitates at different temperatures up to 950 °C. The annealed HoFeO3 nanoparticles have an average crystal size of 10–20 nm (SEM, TEM). UV-Vis spectrum of HoFeO3 sample annealed at 750 °C showed strong UV and Vis absorption with small optical energy gap (Eg = 1.56 eV). In the range temperature of 100–300 K, the HoFeO3 samples showed superparamagnetic behaviour at 5 kOe with high magnetization (Ms = 1.3–2.4 emu/g) and very low susceptibility (χ << 1).

scholarly journals Modeling of magneto-conductivity of bismuth selenide: a topological insulator

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yogesh Kumar ◽  
Rabia Sultana ◽  
Prince Sharma ◽  
V. P. S. Awana
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Crystal ◽  
Single Crystals ◽  
X Ray Diffraction ◽  
Field Range ◽  
X Ray ◽  
Bulk Carriers ◽  
Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

Role of energy-band offset in photo-electrochemical etching mechanism of p-GaN heterostructures

2021 ◽  
Vol 129 (16) ◽  
pp. 165701
Author(s):  
Aqdas Fariza ◽  
Xiaoli Ji ◽  
Yaqi Gao ◽  
Junxue Ran ◽  
Junxi Wang ◽  
...  
Keyword(s):  
Energy Band ◽  
Electrochemical Etching ◽  
Band Offset ◽  
Etching Mechanism ◽  
Energy Band Offset

Quantum Confinement Effects on the Dielectric Constant of Porous Silicon

1992 ◽  
Vol 283 ◽  
Author(s):  
R. Tsu ◽  
L. Ioriatti ◽  
J. F. Harvey ◽  
H. Shen ◽  
R. A. Lux
Keyword(s):  
Dielectric Constant ◽  
Porous Silicon ◽  
Size Effects ◽  
Quantum Confinement ◽  
Electrochemical Etching ◽  
Index Of Refraction ◽  
Quantum Size Effects ◽  
Quantum Size ◽  
Quantum Confinement Effects ◽  
Shallow Impurities

ABSTRACTThe reduction of the dielectric constant due to quantum confinement is studied both experimentally and theoretically. Angle resolved ellipsometry measurements with Ar- and He-Ne-lasers give values for the index of refraction far below what can be accounted for from porosity alone. A modified Penn model to include quantum size effects has been used to calculate the reduction in the static dielectric constant (ε) with extreme confinement. Since the binding energy of shallow impurities depends inversely on ε2, the drastic decrease in the carrier concentration as a result of the decrease in ε leads to a self-limiting process for the electrochemical etching of porous silicon.

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