Investigation on the Threading Dislocations Formed by Lattice Misfits during Initial Stage of Sublimation Growth of 4H-SiC

2020 ◽  
Vol 1004 ◽  
pp. 51-56
Author(s):  
Tai Hee Eun ◽  
Im Gyu Yeo ◽  
Jang Yul Kim ◽  
Seung Seok Lee ◽  
Han Suk Seo ◽  
...  

We investigated the relation between the nucleation of dislocations and the lattice misfits by nitrogen concentration difference between seed and grown crystal during the initial stage of growth. 4H-SiC single crystals were grown with various nitrogen gas flow rates introduced into the crystal growing chamber under the same temperature and pressure to minimize the effect of thermal stress on the nucleation of dislocations. The nitrogen atomic concentrations of grown crystals depended on the introduced nitrogen gas ratios and they highly increased at the very early stage of growth. The generation of new threading dislocations at the interface also was affected by the nitrogen atomic concentrations differences between seed and grown crystals. Very few generated threading dislocations were observed in low nitrogen atomic concentration samples, however nucleation of threading dislocations at the interface were found in high nitrogen atomic concentrations samples. At initial stages of PVT growth process, the generation of threading dislocations induced by lattice misfits originated from nitrogen concentration difference between seed and grown crystals were investigated and found the appropriate nitrogen gas flow rates and profile at the heating and depressurized stage.

Author(s):  
C. Vannuffel ◽  
C. Schiller ◽  
J. P. Chevalier

Recently, interest has focused on the epitaxy of GaAs on Si as a promising material for electronic applications, potentially for integration of optoelectronic devices on silicon wafers. The essential problem concerns the 4% misfit between the two materials, and this must be accommodated by a network of interfacial dislocations with the lowest number of threading dislocations. It is thus important to understand the detailed mechanism of the formation of this network, in order to eventually reduce the dislocation density at the top of the layers.MOVPE growth is carried out on slightly misoriented, (3.5°) from (001) towards , Si substrates. Here we report on the effect of this misorientation on the interfacial defects, at a very early stage of growth. Only the first stage, of the well-known two step growth process, is thus considered. Previously, we showed that full substrate coverage occured for GaAs thicknesses of 5 nm in contrast to MBE growth, where substantially greater thicknesses are required.


2015 ◽  
Vol 87 ◽  
pp. 32-39 ◽  
Author(s):  
S. Komiyama ◽  
Y. Sutou ◽  
K. Oikawa ◽  
J. Koike ◽  
M. Wang ◽  
...  

2018 ◽  
Vol 922 ◽  
pp. 92-97 ◽  
Author(s):  
Sotaro Baba ◽  
Tomoyo Goto ◽  
Sung Hun Cho ◽  
Tohru Sekino

The effect of nitrogen gas flow rate on the morphology of silicon nitride fibers obtained via carbothermal nitridation heat treatment method was investigated. A precursor containing silicon, oxygen and carbon was obtained by a sol-gel method from a mixture of tetraethyl orthosilicate, polyvinyl alcohol, H2O and ethanol. A white wool-like product was obtained by heat treating the precursor placed in an alumina crucible under a 0.5 MPa nitrogen gas pressure at 1500oC with different nitrogen gas flow rates. The mass-based production rates of the samples obtained from the precursor powder were 20-30% for the different nitrogen gas flow rates. X-ray diffraction analysis revealed that the samples contained α-Si3N4 as the major phase along with β-Si3N4, Si2N2O and a small amount of amorphous product as minor phases. Unique twisted fibers with diameters of several hundreds of nanometers were found among the straight fibers by SEM observation. Elemental analysis using energy dispersive X-ray spectroscopy indicated that silicon and nitrogen were contained in the twisted fibers along with approximately 68 at.% of oxygen and several at.% of aluminum, which might have come from the crucible material. The SiAlON-like structures might have been formed by the partial dissolution of Al and O in the Si3N4 fibers. It was considered that the twisted morphology of some fibers might be formed by co-existing of β-SiAlON and/or amorphous phase regions in the Si3N4 fiber and resultant distortion of the fibers.


Electronics ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1099 ◽  
Author(s):  
Song-Yi Ahn ◽  
Kyung Park ◽  
Daehwan Choi ◽  
Jozeph Park ◽  
Yong Joo Kim ◽  
...  

In the present study, the effects of nitrogen incorporation on the transition of a p-type copper oxide semiconductor are investigated. The properties of sputtered copper oxide and nitrogen-incorporated copper oxide are evaluated and compared at various nitrogen gas flow rates. The results indicate that the addition of nitrogen results in an increased optical bandgap, accompanied by significantly reduced tail states compared to pristine copper oxide. In addition, X-ray diffraction and X-ray photoelectron spectroscopy reveal that the incorporation of nitrogen stimulates the transition from copper (II) oxide to copper (I) oxide.


2008 ◽  
Vol 8 (5) ◽  
pp. 2540-2543 ◽  
Author(s):  
S. M. Kang ◽  
S. G. Yoon ◽  
S.-W. Kim ◽  
D. H. Yoon

Amorphous Si (a-Si) quantum dots (QDs) embedded in a silicon nitride film were prepared by a plasma-enhanced chemical vapor deposition (PECVD) technique using gaseous mixtures of silane, hydrogen and nitrogen. We observed that the Si QDs had an amorphous structure from the Raman spectroscopy measurement. The Fourier transform infrared (FTIR) spectra showed that the relative transmittance of the SiH bands decreased, but that of the NH bands increased, with increasing nitrogen flow rate. During the deposition of SiNx, the number of dangling bonds of silicon acting as nucleation sites increased. As the hydrogen flow rate increased the growth rate decreased, due to the reduction in the hydrogen partial pressure. The hydrogen and nitrogen gas flow rates were found to be important parameters for determining the size of the a-Si QDs. In addition, we observed that the PL peak shifted toward a higher energy with increasing hydrogen and nitrogen gas flow rates, which was attributed to the increase in the quantum confinement effect in the a-Si QDs.


2011 ◽  
Vol 39 (6) ◽  
pp. 1103-1110 ◽  
Author(s):  
J. E. Ritchie ◽  
A. B. Williams ◽  
C. Gerard ◽  
H. Hockey

In this study, we evaluated the performance of a humidified nasal high-flow system (Optiflow™, Fisher and Paykel Healthcare) by measuring delivered FiO2 and airway pressures. Oxygraphy, capnography and measurement of airway pressures were performed through a hypopharyngeal catheter in healthy volunteers receiving Optiflow™ humidified nasal high flow therapy at rest and with exercise. The study was conducted in a non-clinical experimental setting. Ten healthy volunteers completed the study after giving informed written consent. Participants received a delivered oxygen fraction of 0.60 with gas flow rates of 10, 20, 30, 40 and 50 l/minute in random order. FiO2, FEO2, FECO2 and airway pressures were measured. Calculation of FiO2 from FEO2 and FECO2 was later performed. Calculated FiO2 approached 0.60 as gas flow rates increased above 30 l/minute during nose breathing at rest. High peak inspiratory flow rates with exercise were associated with increased air entrainment. Hypopharyngeal pressure increased with increasing delivered gas flow rate. At 50 l/minute the system delivered a mean airway pressure of up to 7.1 cmH2O. We believe that the high gas flow rates delivered by this system enable an accurate inspired oxygen fraction to be delivered. The positive mean airway pressure created by the high flow increases the efficacy of this system and may serve as a bridge to formal positive pressure systems.


Author(s):  
Z. Insepov ◽  
R. J. Miller

Propagation of Rayleigh traveling waves from a gas on a nanotube surface activates a macroscopic flow of the gas (or gases) that depends critically on the atomic mass of the gas. Our molecular dynamics simulations show that the surface waves are capable of actuating significant macroscopic flows of atomic and molecular hydrogen, helium, and a mixture of both gases both inside and outside carbon nanotubes (CNT). In addition, our simulations predict a new “nanoseparation” effect when a nanotube is filled with a mixture of two gases with different masses or placed inside a volume filled with a mixture of several gases with different masses. The mass selectivity of the nanopumping can be used to develop a highly selective filter for various gases. Gas flow rates, pumping, and separation efficiencies were calculated at various wave frequencies and phase velocities of the surface waves. The nanopumping effect was analyzed for its applicability to actuate nanofluids into fuel cells through carbon nanotubes.


Sign in / Sign up

Export Citation Format

Share Document