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.

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 and Characterization of Free-standing Porous Silicon Films with High Porosity

1998 ◽  
Vol 14 (07) ◽  
pp. 577-580
Author(s):  
Xu Dong-Sheng ◽  
◽  
Guo Guo-Lin ◽  
Gui Lin-Lin ◽  
Zhang Bo-Rui ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Silicon Films ◽  
High Porosity ◽  
Free Standing

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.

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.

Femtosecond Nonlinear Transmission Study of Free-Standing Porous Silicon Films

1995 ◽  
Vol 405 ◽  
Author(s):  
V. Klimov ◽  
D. Mcbranch ◽  
V. Karavanskii
Keyword(s):  
Porous Silicon ◽  
Transient Absorption ◽  
Energy Levels ◽  
Silicon Films ◽  
Spectral Structure ◽  
Relaxation Dynamics ◽  
Free Standing ◽  
Pump And Probe ◽  
Transmission Study ◽  
Nonlinear Signal

AbstractLarge photo-induced absorption signals were observed in free standing porous silicon films in the spectral range from 1.1 to 2.5 eV using a femtosecond pump and probe technique. The measured nonlinear signal has a very fast component with relaxation constants from 800 fs to tens of picoseconds superimposed on the slow-relaxing thermal background. The spectral structure and relaxation dynamics of the short-lived component of transient absorption show the presence of molecular-like Si complexes with well defined energy levels and spectrally uniform picosecond relaxation dynamics.

Absorption and luminescence studies of free-standing porous silicon films

1994 ◽  
Vol 49 (8) ◽  
pp. 5386-5397 ◽  
Author(s):  
Y. H. Xie ◽  
M. S. Hybertsen ◽  
William L. Wilson ◽  
S. A. Ipri ◽  
G. E. Carver ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Silicon Films ◽  
Free Standing

scholarly journals Lift-off of Free-standing Layers in the Kerfless Porous Silicon Process

2013 ◽  
Vol 38 ◽  
pp. 919-925 ◽  
Author(s):  
Sarah Kajari-Schröder ◽  
Jörg Käsewieter ◽  
Jan Hensen ◽  
Rolf Brendel
Keyword(s):  
Porous Silicon ◽  
Free Standing ◽  
Lift Off

Dispersive Fourier Transform Spectroscopy Of Free-Standing Porous Silicon Films

1997 ◽  
Vol 486 ◽  
Author(s):  
J. Salonen ◽  
K. Saarinen ◽  
J. Peura ◽  
J. Vilnikanoja ◽  
I. Salomaa ◽  
...  
Keyword(s):  
Refractive Index ◽  
Fourier Transform ◽  
Porous Silicon ◽  
Absorption Coefficient ◽  
Optical Constants ◽  
Fourier Transform Spectroscopy ◽  
Silicon Films ◽  
Spectral Variation ◽  
Free Standing ◽  
Dispersive Fourier Transform Spectroscopy

AbstractWe have investigated optical constants of free-standing porous silicon films by dispersive Fourier transform spectroscopy (DFTS) in the NIR-VIS range. This allows the spectral variation of both the absorption coefficient and the refractive index of a material to be determined from the measurements of the attenuation and phase shift imposed on an electromagnetic wave by its interaction with a specimen. Using these optical constants, we have studied the complex dielectric function and the complex conductivity. To avoid the additive error in the absorption spectra arising from the pseudocoherence, we measured the transmission spectra by conventional Fourier transform spectroscopy (FTS). Using the refraction spectrum derived from the DFTS measurements, we have corrected for reflection losses in calculation of the absorption spectrum from the FTS transmission spectrum. The changes in the absorption coefficient and the refractive index due to oxidation, which is the most common aging phenomenon in porous silicon, have been studied using samples with different types of oxidization.

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