Reduction of Dislocation Density of SiC Crystals Grown on Seeds after H2 Etching

2017 ◽  
Vol 897 ◽  
pp. 19-23 ◽  
Author(s):  
Xiu Fang Chen ◽  
Fu Sheng Zhang ◽  
Xiang Long Yang ◽  
Yan Peng ◽  
Xue Jian Xie ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Surface Morphology ◽  
Surface Damage ◽  
Subsurface Damage ◽  
Bulk Crystals ◽  
Force Microscopy ◽  
Seed Surface ◽  
Atomic Force ◽  
Order Of Magnitude ◽  
Band Contrast

Three-inch 6H-SiC bulk crystals were grown by the PVT method on the seeds processed by different treatments. The influences of seed surface morphology and subsurface damage on the dislocation density were investigated. The seed surface morphology was characterized by atomic force microscopy (AFM). The extent of the subsurface damage was estimated by electron back-scattered diffraction (EBSD) and Band Contrast (BC) value. The distribution and density of the dislocations were observed by optical microscopy (OM). The results showed that the pit density performed by H2 1400°C etching was nearly one order of magnitude lower than that by mechanical polishing (MP) process. So H2 etching processed at 1400°C for 2h could completely remove the subsurface damage, compared with the MP process with the deep surface damage.

Etching of 4° and 8° 4H-SiC Using Various Hydrogen-Propane Mixtures in a Commercial Hot-Wall CVD Reactor

2007 ◽  
Vol 556-557 ◽  
pp. 513-516 ◽  
Author(s):  
Kok Keong Lew ◽  
Brenda L. VanMil ◽  
Rachael L. Myers-Ward ◽  
Ronald T. Holm ◽  
Charles R. Eddy ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Partial Pressure ◽  
Growth Temperature ◽  
Chemical Vapor ◽  
Surface Damage ◽  
Step Bunching ◽  
Force Microscopy ◽  
Atomic Force ◽  
Stepped Surface ◽  
Higher Temperature

Hydrogen etching of 4H-SiC has been performed in a hot-wall chemical vapor deposition reactor to reduce surface damage and to create a bilayer-stepped surface morphology, optimal for initiation of growth on 4H-SiC substrates offcut 4° and 8° towards the <11-20> direction. To understand how step bunching evolves during the ramp to growth temperature, samples were etched ending at temperatures from 1400 to 1580°C under 0, 2 or 10 sccm of propane (C3H8) addition to hydrogen. Initial exploratory growth of 5 μm thick epilayers on the 4° etched surfaces are also discussed. Atomic force microscopy (AFM) and Nomarski microscopy were employed to investigate changes in the surface morphology. The 8° substrates subjected to H2-C3H8 etching up to growth temperature routinely exhibited bilayer steps. However, when the 4° substrates were etched with a 10 sccm C3H8 flow, considerable step bunching was observed. At 1450°C, with a 10 sccm of C3H8 flow (partial pressure is 1.25x10-5 bar), step bunching started with the formation of ribbon-like steps. Progression to higher temperature etches have shown the coalescence of the ribbons into larger macro-steps up to 30 nm in height. Etching 4° substrates under 2 sccm of C3H8 (partial pressure is 2.5x10-6 bar) or in pure H2 up to 1500°C results in minimal step bunching.

Etching Treatment Effect on Surface Morphology of Dental Structures

2017 ◽  
Vol 68 (11) ◽  
pp. 2700-2703 ◽  
Author(s):  
Kamel Earar ◽  
Vasile Iulian Antoniac ◽  
Sorana Baciu ◽  
Simion Bran ◽  
Florin Onisor ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Surface Morphology ◽  
Phosphoric Acid ◽  
Human Teeth ◽  
Strong Bond ◽  
Force Microscopy ◽  
Atomic Force ◽  
Human Dentine ◽  
Dental Surface ◽  
Scanning Electron

This study examined and compared surface of human dentine after acidic etching with hydrogen peroxide, phosphoric acid liquid and gel. Surface demineralization of dentin is necessary for a strong bond of adhesive at dental surface. Split human teeth were used. After application of mentioned substances at dentin level measures of the contact angle and surface morphology were employed. Surface morphology was analyzed with the help of scanning electron microscopy and atomic force microscopy. Liquid phosphoric acid yielded highest demineralization showing better hydrophobicity than the rest, thus having more contact surface. Surface roughness are less evident and formed surface micropores of 4 �m remained open after wash and air dry providing better adhesive canalicular penetration and subsequent bond.

scholarly journals Steady state charge conduction through solution processed liquid crystalline lanthanide bisphthalocyanine films

2019 ◽  
Vol 23 (11n12) ◽  
pp. 1603-1615
Author(s):  
Chandana Pal ◽  
Isabelle Chambrier ◽  
Andrew N. Cammidge ◽  
A. K. Sharma ◽  
Asim K. Ray
Keyword(s):  
Metal Ions ◽  
Liquid Crystalline ◽  
Microscopy Study ◽  
Individual Characteristics ◽  
Central Metal ◽  
Force Microscopy ◽  
Atomic Force ◽  
Double Decker ◽  
Order Of Magnitude ◽  
Chain Lengths

In-plane electrical characteristics of non-peripherally octyl(C[Formula: see text]H[Formula: see text]- and hexyl(C[Formula: see text]H[Formula: see text]-substituted liquid crystalline (LC) double decker lanthanide bisphthalocyanine (LnPc[Formula: see text] complexes with central metal ions lutetium (Lu), and gadolinium (Gd) have been measured in thin film formulations on interdigitated gold (Au) electrodes for the applied voltage ([Formula: see text] range of [Formula: see text]. The conduction mechanism is found to be Ohmic within the bias of [Formula: see text] while the bulk limited Poole–Frenkel mechanism is responsible for the higher bias. The compounds show individual characteristics depending on the central metal ions, substituent chain lengths and their mesophases. Values of 67.55 [Formula: see text]cm[Formula: see text] and 42.31 [Formula: see text]cm[Formula: see text] have been obtained for room temperature in-plane Ohmic conductivity of as-deposited octyl lutetium (C[Formula: see text]LuPc[Formula: see text] and hexyl gadolinium (C[Formula: see text]GdPc[Formula: see text] films, respectively while C[Formula: see text]GdPc[Formula: see text] films exhibit nearly two orders of magnitude smaller conductivity. On annealing at 80[Formula: see text]C, Ohmic conductivities of C[Formula: see text]LuPc[Formula: see text] and C[Formula: see text]GdPc[Formula: see text] are found to have increased but the conductivity of C[Formula: see text]GdPc[Formula: see text] decreased by more than one order of magnitude to 1.5 [Formula: see text]cm[Formula: see text]. For physical interpretation of the charge transport behavior of these three molecules, their UV-vis optical absorption spectra in the solution and in as-deposited and annealed solid phases and atomic force microscopy study have been performed. It is believed that both orientation and positional reorganizations are responsible, depending upon the size of the central ion and side chain length.

Surface morphology of As-deposited and laser-damaged dielectric mirror coatings studied in-situ by atomic force microscopy

1992 ◽  
Author(s):  
Mark R. Kozlowski ◽  
Michael C. Staggs ◽  
Mehdi Balooch ◽  
Robert J. Tench ◽  
Wigbert J. Siekhaus
Keyword(s):  
Atomic Force Microscopy ◽  
Surface Morphology ◽  
Force Microscopy ◽  
Dielectric Mirror ◽  
Atomic Force

Surface morphology studies on sublimation grown GaN by atomic force microscopy

1999 ◽  
Vol 200 (3-4) ◽  
pp. 348-352 ◽  
Author(s):  
R.S Qhalid Fareed ◽  
S Tottori ◽  
K Nishino ◽  
S Sakai
Keyword(s):  
Atomic Force Microscopy ◽  
Surface Morphology ◽  
Force Microscopy ◽  
Atomic Force

Defect-Engineered Graded GexSi1-x Buffers on Si (001) with Extreme Low Threading Dislocation Density

1995 ◽  
Vol 378 ◽  
Author(s):  
G. Kissinger ◽  
T. Morgenstern ◽  
G. Morgenstern ◽  
H. B. Erzgräber ◽  
H. Richter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Dislocation Density ◽  
Threading Dislocation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Threading Dislocation Density

AbstractStepwise equilibrated graded GexSii-x (x≤0.2) buffers with threading dislocation densities between 102 and 103 cm−2 on the whole area of 4 inch silicon wafers were grown and studied by transmission electron microscopy, defect etching, atomic force microscopy and photoluminescence spectroscopy.

Stress Relaxation in Uniquely Oriented SiGe/Si Epitaxial Layers

1999 ◽  
Vol 594 ◽  
Author(s):  
M. E. Ware ◽  
R. J. Nemanich
Keyword(s):  
Stress Relaxation ◽  
Surface Morphology ◽  
Strain Relaxation ◽  
Epitaxial Layers ◽  
Misfit Dislocations ◽  
Strained Layers ◽  
Force Microscopy ◽  
Si Substrates ◽  
Atomic Force ◽  
Deposited Films

AbstractThis study explores stress relaxation of epitaxial SiGe layers grown on Si substrates with unique orientations. The crystallographic orientations of the Si substrates used were off-axis from the (001) plane towards the (111) plane by angles, θ = 0, 10, and 22 degrees. We have grown 100nm thick Si(1−x) Ge(x) epitaxial layers with x=0.3 on the Si substrates to examine the relaxation process. The as-deposited films are metastable to the formation of strain relaxing misfit dislocations, and thermal annealing is used to obtain highly relaxed films for comparison. Raman spectroscopy has been used to measure the strain relaxation, and atomic force microscopy has been used to explore the development of surface morphology. The Raman scattering indicated that the strain in the as-deposited films is dependent on the substrate orientation with strained layers grown on Si with 0 and 22 degree orientations while highly relaxed films were grown on the 10 degree substrate. The surface morphology also differed for the substrate orientations. The 10 degree surface is relatively smooth with hut shaped structures oriented at predicted angles relative to the step edges.

Chromic Polydiacetylene Single Crystals: Atomic Force Microscopy Studies

1995 ◽  
Vol 413 ◽  
Author(s):  
V. Shivshankar ◽  
C. Sung ◽  
J. Kumar ◽  
S. K. Tripathy ◽  
D. J. Sandman
Keyword(s):  
Atomic Force Microscopy ◽  
Surface Morphology ◽  
Single Crystals ◽  
Ambient Conditions ◽  
Free Standing ◽  
Force Microscopy ◽  
Sensor Performance ◽  
Atomic Force ◽  
Variable Surface

ABSTRACTWe have studied the surface morphology of free standing single crystals of thermochromic polydiacetylenes (PDAs), namely, ETCD and IPUDO (respectively, the ethyl and isopropyl urethanes of 5,7-dodecadiyn-1,12-diol), by Atomic Force Microscopy (AFM) under ambient conditions. Micron scale as well as molecularly resolved images were obtained. The micron scale images indicate a variable surface, and the molecularly resolved images show a well defined 2-D lattice that is interpreted in terms of molecular models and known crystallographic data. Thereby information about surface morphology, which is crucial to potential optical device or chromic sensor performance is available. We also report the observation of a “macroscopic shattering” of the IPUDO monomer crystal during in-situ UV polymerization studies.

Sign in / Sign up

Export Citation Format

Share Document