Optical Properties of Free-Standing Ultrahigh Porosity Silicon Films Prepared by Supercritical Drying

1996 ◽  
Vol 452 ◽  
Author(s):  
J. Von Behren ◽  
P. M. Fauchet ◽  
E. H. Chimowitz ◽  
C. T. Lira
Keyword(s):  
Porous Silicon ◽  
Electrochemical Etching ◽  
Supercritical Drying ◽  
Silicon Films ◽  
Index Of Refraction ◽  
Free Standing ◽  
Crystal Silicon ◽  
Si Substrates ◽  
Type C ◽  
P Type

AbstractHighly luminescent free-standing porous silicon thin films of excellent optical quality have been manufactured by using electrochemical etching and lift-off steps combined with supercritical drying. One to 50 μm thick free-standing layers made from highly (p+) and moderately (p) Boron doped single crystal silicon (c-Si) substrates have been produced with porosities (P) up to 95 %. The Fabry-Pérot fringes observed in the transmission and photoluminescence (PL) spectra are used to determine the refractive index. At the highest P the index of refraction is below 1.2 from the IR to 2 eV. The absorption coefficients follow a nearly exponential behavior in the energy range from 1.2 eV and 4 eV. The porosity corrected absorption spectra of free-standing films made from p type c-Si substrates are blue shifted with respect to those prepared from p+ substrates. For P > 70 % a blue shift is also observed in PL. At equal porosities the luminescence intensities of porous silicon films made from p+ and p type c-Si are different by one order of magnitude.

Preparation, Properties and Applications of Free-Standing Porous Silicon Films

1994 ◽  
Vol 358 ◽  
Author(s):  
J. Von Behren ◽  
L. Tsybeskov ◽  
P. M. Fauchet
Keyword(s):  
Porous Silicon ◽  
Near Infrared ◽  
Electrochemical Etching ◽  
Supercritical Drying ◽  
Silicon Films ◽  
Index Of Refraction ◽  
High Porosity ◽  
Large Area ◽  
Free Standing ◽  
Lift Off

ABSTRACTUsing special electrochemical etching and lift-off steps, we have fabricated large-area freestanding porous silicon films in the thickness range from 0.1 μm to 50 μm. Their transmission is near 100% in the near infrared which is indicative of very high porosity/low index of refraction films. These optically flat and homogeneous films exhibit no surface and bulk scattering, despite the fact that they did not undergo supercritical drying. The relationship between the absorption coefficient, the luminescence spectrum, and the chemical and structural properties is examined as a function of preparation and post-treatment conditions. Because of their superior optical properties, these films are suitable for many device applications.

scholarly journals Room-Temperature H2 Gas Sensing Characterization of Graphene-Doped Porous Silicon via a Facile Solution Dropping Method

2017 ◽  
Author(s):  
Nu Si A Eom ◽  
Hong-Baek Cho ◽  
Yoseb Song ◽  
Woojin Lee ◽  
Tohru Sekino ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Gas Sensor ◽  
Room Temperature ◽  
Gas Sensing ◽  
Electrochemical Etching ◽  
Sensor Material ◽  
Sensing Mechanism ◽  
Si Substrates ◽  
H2 Sensor ◽  
P Type

In this study, a graphene-doped porous silicon (G-doped/p-Si) substrate for low ppm H2 gas detection by an inexpensive synthesis route was proposed as a potential noble graphene-based gas sensor material and to understand the sensing mechanism. The G-doped/p-Si gas sensor was synthesized by a simple capillary force-assisted solution dropping method on p-Si substrates, whose porosity was generated through an electrochemical etching process. G-doped/p-Si was fabricated with various graphene concentrations and exploited as a H2 sensor operated at room temperature. The sensing mechanism of the sensor with/without graphene decoration on p-Si was proposed to elucidate the synergetic gas sensing effect generated from the interface between the graphene and p-type silicon.

Tem Study of Porous Silicon Fabricated from N- and P-Type Doped Polycrystalline Films

1996 ◽  
Vol 452 ◽  
Author(s):  
L. Haji ◽  
Y. Le Thomas ◽  
F. Chane Che Lai ◽  
P. Joubert
Keyword(s):  
Porous Silicon ◽  
Pore Formation ◽  
Single Crystal Silicon ◽  
Extended Defects ◽  
Crystal Silicon ◽  
Cross Sectional ◽  
Si Substrates ◽  
Transmission Electron ◽  
Polycrystalline Silicon Films ◽  
P Type

AbstractThe formation of porous silicon (PS) from n/p, n+/p and p+/n structures carried from polycrystalline silicon films (poly-Si) deposited on single crystal silicon (c-Si) substrates was studied by cross-sectional transmission electron microscopy. Our results clearly show that the pore formation in such structures involve the extended defects of the poly-Si film. The role played by these defects depends on the doping type and level, and on whether the anodization is performed under illumination or not.

scholarly journals Photo and electroluminescence of porous silicon layers

BIBECHANA ◽  
2012 ◽  
Vol 8 ◽  
pp. 46-52
Author(s):  
E Haji-Ali
Keyword(s):  
Porous Silicon ◽  
Light Emission ◽  
Electrochemical Cell ◽  
Electrochemical Etching ◽  
Light Illumination ◽  
Porous Layers ◽  
Si Substrates ◽  
Orange Yellow ◽  
Intense Light ◽  
P Type

Porous silicon layers were prepared by both chemical and electrochemical methods on n- and ptype Si substrates. In the former technique, light emission was obtained from p-type and n-type samples. It was found that intense light illumination during the preparation process was essential for PSi formation on n-type substrates.An efficient electrochemical cell with some useful features was designed for electrochemical etching of silicon. Various preparation parameters were studied and photoluminescence emissions ranging from dark red to light blue were obtained from PSi samples prepared on p-type substrates. N-type samples produced emissions ranging from dark red to orange-yellow. Electroluminescence of porous silicon samples showed that the color of the emission was the same as the photoluminescence color of the sample, and its intensity and duration depended on the current density passed through the sample. The effects of exposure of samples to air, storage in vacuum, and heat-treatment in air on luminescence intensity of the samples and preparation of patterned porous layers were also studied.Keywords: Porous silicon layers; photoluminescence; electroluminescenceDOI: http://dx.doi.org/10.3126/bibechana.v8i0.4897  BIBECHANA 8 (2012) 46-52

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.

Strongly Superlinear Light Emission and Large Induced Absorption in Oxidized Porous Silicon Films

1998 ◽  
Vol 536 ◽  
Author(s):  
H. Koyama ◽  
P. M. Fauchet
Keyword(s):  
Porous Silicon ◽  
Thermal Effects ◽  
Light Emission ◽  
Laser Intensity ◽  
Excitation Intensity ◽  
Silicon Films ◽  
Free Standing ◽  
Induced Absorption ◽  
Cw Laser ◽  
Oxidized Porous Silicon

AbstractThe optical properties of oxidized free-standing porous silicon films excited by a cw laser have been investigated. It is found that samples oxidized at 800–950 °C show a strongly superlinear light emission at an excitation intensity of ∼10 W/cm2. This emission has a peak at 900–1100 nm and shows a blueshift as the oxidation temperature is increased. These samples also show a very large induced absorption, where the transmittance is found to decrease reversibly by ≤99.7 %.The induced absorption increases linearly with increasing pump laser intensity. Both the superlinear emission and the large induced absorption are quenched when the samples are attached to materials with a higher thermal conductivity, suggesting that laser-induced thermal effects are responsible for these phenomena.

Structural, Surface Morphological and Photoluminescence Properties of Nanostructured Porous Silicon Material for Optoelectronics Application

2012 ◽  
Vol 584 ◽  
pp. 290-294 ◽  
Author(s):  
Jeyaprakash Pandiarajan ◽  
Natarajan Jeyakumaran ◽  
Natarajan Prithivikumaran
Keyword(s):  
Porous Silicon ◽  
Current Density ◽  
Light Emission ◽  
Electrochemical Etching ◽  
Light Emitting Diode ◽  
Radiative Transition ◽  
Sem Images ◽  
Optoelectronic Application ◽  
Gap Opening ◽  
P Type

The promotion of silicon (Si) from being the key material for microelectronics to an interesting material for optoelectronic application is a consequence of the possibility to reduce its device dimensionally by a cheap and easy technique. In fact, electrochemical etching of Si under controlled conditions leads to the formation of nanocrystalline porous silicon (PS) where quantum confinement of photo excited carriers and surface species yield to a band gap opening and an increased radiative transition rate resulting in efficient light emission. In the present study, the nanostructured PS samples were prepared using anodic etching of p-type silicon. The effect of current density on structural and optical properties of PS, has been investigated. XRD studies confirm the presence of silicon nanocrystallites in the PS structure. By increasing the current density, the average estimated values of grain size are found to be decreased. SEM images indicate that the pores are surrounded by a thick columnar network of silicon walls. The observed PL spectra at room temperature for all the current densities confirm the formation of PS structures with nanocrystalline features. PL studies reveal that there is a prominent visible emission peak at 606 nm. The obtained variation of intensity in PL emission may be used for intensity varied light emitting diode applications. These studies confirm that the PS is a versatile material with potential for optoelectronics application.

Optical studies of the structure of porous silicon films formed in p-type degenerate and non-degenerate silicon

1984 ◽  
Vol 17 (35) ◽  
pp. 6535-6552 ◽  
Author(s):  
C Pickering ◽  
M I J Beale ◽  
D J Robbins ◽  
P J Pearson ◽  
R Greef
Keyword(s):  
Porous Silicon ◽  
Silicon Films ◽  
Optical Studies ◽  
P Type

Porous Silicon Morphology: Photo-Electrochemically Etched by Different Laser Wavelengths

2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Shereen M. Faraj ◽  
Shaimaa M. Abd Al-Baqi ◽  
Nasreen R. Jber ◽  
Johnny Fisher
Keyword(s):  
Porous Silicon ◽  
Electrochemical Etching ◽  
Diode Lasers ◽  
Focus Of Attention ◽  
Blue Laser ◽  
Uniform Structure ◽  
Porous Layers ◽  
Current Densities ◽  
P Type ◽  
532 Nm

Porous silicon (PS) has become the focus of attention in upgrading silicon for optoelectronics. In this work, various structures were produced depending on the formation parameters by photo-electrochemical etching (PECE) process of n- and p-type silicon wafer at different time durations (5–90 mins) and different current densities (5, 15, and 20 mA/cm2) for each set of time durations. Diode lasers of 405 nm, 473 nm, and 532 nm wavelengths, each 50 mW power, were used to illuminate the surface of the samples during the etching process. The results showed that controlled porous layers were achieved by using blue laser, giving uniform structure which can make it possible to dispense with expensive methods of patterning the silicon.

Porous Silicon as a Sacrificial Material for Microstructures Fabrication

1999 ◽  
Vol 605 ◽  
Author(s):  
M. Morel ◽  
M. Le Berre ◽  
V. Lysenko ◽  
G. Delhomme ◽  
A. Dittmar ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Electrochemical Etching ◽  
Sacrificial Layer ◽  
Formation Rate ◽  
Free Standing ◽  
Wide Range ◽  
Silicon Bulk ◽  
Reduced Costs ◽  
Optimized Conditions ◽  
Koh Etching

AbstractPorous silicon (PS) is generated by electrochemical etching in hydrofluoric acid (HF). Recently porous silicon has been applied to micromachining and micro-devices as an alternate material, this material being used as a sacrificial layer. This technology competes with conventional techniques like surface and bulk micromachining regarding its speed, simplicity and reduced costs. A wide range of microstructures and free-standing structures can be fabricated with a large freedom of design in relation to the isotropic behavior of the etching. A sacrificial layer may be realized fast over varying thickness (PS formation rate 45 μm/h compared to silicon bulk micromachining rate 20 μm/h for KOH etching).This contribution is devoted to the materials aspects of patterning and processing: we will show how basic microstructures (trenches, polysilicon cantilevers, polysilicon free-standing membranes) may be fabricated using a very simple process based on a single photolithography. The important points are the choice of the mask, porous silicon properties as a function of its formation parameters and the choice of the solution removing the sacrificial layer. The morphology and porosity of the porous silicon layers are indeed mainly determined by the electrolyte composition and by the current density for a given substrate type. Optimized conditions (HF 15% and 80 mA/cm2) lead us to an appropriate porous silicon. Finally the applicability of this technology for various microsensors will be underlined.

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