Porous 3C-SiC Research Articles

Surface morphology effects on the mechanical and electronic properties of halogenated porous 3C-SiC: A DFT study

Silicon carbide nanostructures have been widely studied due to their potential technological applications. However, the theoretical characterization, especially the effect of the surface on the mechanical properties of this material is still underexplored. In this work, we report the electronic and mechanical properties of 3C-SiC nanopores with different pore surfaces and different passivation schemes using a density functional theory approach and the supercell technique. The nanopores were modeled by removing columns of atoms in the [001] direction, thus creating four types of pores, two with an Only C or Si pore and two with a C or Si-Rich pore surface. All surfaces were passivated with hydrogen, then some atoms of H were replaced with fluorine and chlorine. Results show that pores with a higher concentration of C on the surface have a larger bandgap compared with the Si cases. Moreover, only a few changes can be observed due to passivation. For the mechanical properties the Bulk and Young’s modulus were calculated and show that the Only C structures were the most brittle and, for almost all the pores, the H + Cl passivation improve the Bulk modulus.

Growth mechanism of porous 3C–SiC films prepared via laser chemical vapor deposition

Porous SiC film is an excellent electrode material for robust micro-supercapacitors used in extremely harsh environments. In one of our previous studies, porous 3C–SiC film with high areal capacitance and high deposition rate was prepared via laser chemical vapor deposition (LCVD). However, it is still urgent to explore the formation mechanism of porous structures using LCVD. In this study, the microstructure of the porous cubic SiC film prepared via LCVD was analyzed in detail using scanning and transmission electron microscopy techniques. The growth mechanism of the deposits has been proposed according to the “growth competing theory” and “shadow effect theory.”

Modeling the effects of Si-X (X = F, Cl) bonds on the chemical and electronic properties of Si-surface terminated porous 3C-SiC

Porous silicon carbide offers a great potential as a sensor material for applications in medicine and energetics; however, the theoretical chemical characterization of its surface is almost nonexistent, and a correct understanding of its chemical properties could lead to the development of better applications of this nanostructure. Hence, a study of the effects of different passivation agents on the structure and electronic properties of porous silicon carbide by means of density functional theory and the supercell technique was developed. The porous structures were modeled by removing columns of atoms of an otherwise perfect SiC crystal in the [001] direction, so that the porous structure exhibits a surface exclusively composed of Si atoms (Si-rich) using different surface passivation agents, such as hydrogen (H), fluoride (F) and chloride (Cl). The results demonstrate that all of the passivation schemes exhibit an irregular band gap energy evolution due to a hybridization change of the surface. The structural analysis shows a great dependence of the bond characteristics on the electronegativity of the bonded atoms, and all of the structural and electronic changes could be explained due to steric effects. These results could be important in the characterization of pSiC because they provide insight into the most stable surface configurations and their electronic structures.

Hydrogen sensing characteristics of vertical type hydrogen sensors based on porous 3C-SiC with catalyst materials

The hydrogen-sensing characteristics of porous 3C-SiC (p-SiC) with different catalyst metals were investigated. The scanning electron microscopy results confirm that the 3C-SiC film has a porous structure with a pore size of 20---30 nm. Hydrogen sensing behavior of Pd/p-SiC was analyzed as a function of hydrogen concentration by current---voltage (I---V) and źI-t methods under steady state and transient conditions. The Pd was used as a Schottky contact and detection material. The Pt and Au catalyst metals were deposited on Pd layer to increase the hydrogen sensing characteristics. The change in current was monitored in the range of 210---610 ppm hydrogen concentrations. The deposited Pt was more sensitive to hydrogen gas than the Pd and Au catalyst metals. It is evaluated that the hydrogen sensing properties of porous 3C-SiC Schottky-diode can be improved by Pt and Pd catalytic metals.

Fast response hydrogen sensors based on palladium and platinum/porous 3C-SiC Schottky diodes

Porous 3C-SiC (pSiC) samples with an average pore diameter of 30 nm were prepared by electrochemical anodization. Planar type Schottky diodes were fabricated using 1-mm diameter Au contact metal where the Au dot was chemically modified via the sputtering of Pd and Pt for use as a hydrogen catalyst. Changes in the current were monitored with respect to hydrogen concentration in the range of 10–40 ppm with a 3.7 V forward bias. The variations in current in the presence of hydrogen demonstrated that Pd and Pt/Au/pSiC samples have the ability to detect hydrogen. In the case of Pd, the response and recovery time at room temperature were 2.3 and 1.5 s, respectively. A large change in current was observed with the Pd catalyst, and the hydrogen sensing performance improved at high temperatures.

다공성 3C-SiC 기반 저항식 수소센서의 제작과 그 특성

Porous 3C-SiC(pSiC) samples with different pore diameters were prepared from poly crystalline N-type 3C-SiC by electrochemical anodization. The pSiC surface was chemically modified by the sputtering of Pd and Pt nano-particles as a hydrogen catalyst. Changes in resistance were monitored with hydrogen concentrations in the range of 110 ppm - 410 ppm. The variations of the electrical resistance in the presence of hydrogen demonstrated that Pd and Pt-deposited pSiC samples have the ability to detect hydrogen at room temperature. Regardless of the catalyst, the 25 nm pore diameter samples showed good response and recovery properties. However, the 60 nm samples showed unstable and slow response. It was found that the pore size affects the catalyst reaction and consequently, results in changes of the sensitivity to hydrogen.

Characterization of porous cubic silicon carbide deposited with Pd and Pt nanoparticles as a hydrogen sensor

Porous 3C-SiC (pSiC) samples with different pore diameters were prepared from polycrystalline n-type 3C-SiC films by electrochemical anodization using a mixture of HF and ethanol as the electrolyte solution. The pSiC surface was chemically modified via the sputtering of Pd and Pt nanoparticles as a hydrogen catalyst. Changes in the resistance were monitored with respect to hydrogen concentrations in the range of 110–410 ppm. The variations in the electrical resistance at the presence of nitrogen diluted with hydrogen demonstrated that Pd and Pt-deposited pSiC samples have the ability to detect hydrogen. Regardless of the catalyst, the 25 nm pore diameter samples exhibited better response and recovery properties than the 60 nm pore diameter samples. It was found that the pore size affects the catalyst reaction and results in changes in the response factor to hydrogen. A large change in resistivity was observed with the Pd catalyst and the hydrogen sensing performance improved at high temperatures.

질소가 도핑된 다공질 3C-SiC 박막의 열적, 기계적 특성

This paper describes the thermal and mechanical properties of doped thin film 3C-SiC and porous 3C-SiC. In this work, the in-situ doped thin film 3C-SiC was deposited by using atmospheric pressure chemical vapor deposition (APCVD) method at using single-precursor hexamethyildisilane: (HMDS) as Si and C precursors. 0~40 sccm gas was used as doping source. After growing of doped thin film 3C-SiC, porous structure was achieved by anodization process with 380 nm UV-LED. Anodization time and current density were fixed at 60 sec and 7.1 mA/, respectively. The thermal and mechanical properties of the doped porous 3C-SiC was measured by temperature coefficient of resistance (TCR) and nano-indentation, respectively. In the case of 0 sccm, the variations of TCR of thin film and porous 3C-SiC are similar, but TCR conversely changed with increase of flow rate. Maximum young`s modulus and hardness of porous 3C-SiC films were measured to be 276 GPa and 32 Gpa at 0 sccm , respectively.

In-situ 도핑량이 다공성 3C-SiC 박막의 특성에 미치는 영향

This paper describes the elecrtical and optical characteristics of <TEX>$N_2$</TEX> doped porous 3C-SiC films. Polycrystalline 3C-SiC thin films are anodized by <TEX>$HF+C_2H_5OH$</TEX> solution with UV-LED exposure. The growth of in-situ doped 3C-SiC thin films on p-type Si (100) wafers is carried out by using APCVD (atmospheric pressure chemical vapor deposition) with a single-precursor of HMDS (hexamethyildisilane: <TEX>$Si_2(CH_3)_6)$</TEX>. 0 ~ 40 sccm <TEX>$N_2$</TEX> was used for doping. After the growth of doped 3C-SiC, porous 3C-SiC is formed by anodization with <TEX>$7.1\;mA/cm^2$</TEX> current density for anodization time of 60 sec. The average pore diameter is about 30 nm, and etched area is increased with <TEX>$N_2$</TEX> doping rate. These results are attributed to the decrease of crystallinity by <TEX>$N_2$</TEX> doping. Mobility is dramatically decreased in porous 3C-SiC. The band gaps of polycrystalline 3C-SiC films and doped porous 3C-SiC are 2.5 eV and 2.7 eV, respectively.

Characteristics of Porous 3C-SiC Thin Films Formed with Nitrogen Doping Concentrations

This paper describes the characteristics of porous 3C-SiC with in-situ N-doping concentrations. Polycrystalline (poly) 3C-SiC thin films were deposited on p-type Si (100) substrates by APCVD using hexamethyildisilane (HMDS: Si2(CH3)6). The porous 3C-SiC (pSiC) was achieved by anodized with 380 nm UV-LED. The characteristics of the N2 doped pSiC were evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and photo luminescence (PL). Average pore diameter is about 50 nm and etched area was increased with N2 doping rate. These results are attributed to decrease the crystallinity by N2 doping. The band gaps of poly 3C-SiC films and porous 3C-SiC films were 2.5 eV and 2.7 eV, respectively.

양극산화법과 UV-LED를 이용한 다공성 3C-SiC 박막 형성

This paper describes the formation of porous 3C-SiC by anodization. 3C-SiC thin films were deposited on p-type Si(100) substrates by APCVD using HMDS(Hexamethyildisilane: ). UV-LED(380 nm) was used as a light source. The surface morphology was observed by SEM and the pore size was increased with increase of current density. Pore diameter of 70 90 nm was achieved at 7.1 mA/cm current density and 90 sec anodization time. FT-IR was conducted for chemical bonding of thin film and porous 3C-SiC. The Si-H bonding was observed in porous 3C-SiC around wavenumber 2100 cm. PL shows the band gap enegry of thin film(2.5 eV) and porous 3C-SiC(2.7 eV).

Microstructure and infrared spectral properties of porous polycrystalline and nanocrystalline cubic silicon carbide

We investigated the structural and infrared spectral properties of porous polycrystalline 3C-SiC and 3C-SiC nanoparticles produced via electrochemical method. The porous sample consisted of parallel nanowires with periodic beadlike structures. It exhibited infrared spectral features quite different from that of single crystal. The 3C-SiC crystallites with an average size of 4 nm showed simple surface chemistry with the surfaces well passivated by dissociation of surrounding water molecules. Our result explains the distinctive optical properties in porous polycrystalline and nanocrystalline 3C-SiC and reveals the crucial conditions for quantum confinement photoluminescence to arise.

Interface Defects in n-Type 3C-SiC/SiO&lt;sub&gt;2&lt;/sub&gt;: An EPR Study of Oxidized Porous Silicon Carbide Single Crystals

The defects at the 3C-SiC/SiO2 interface have been studied by X-band EPR spectroscopy in oxidized porous 3C-SiC. One interface defect is detected; its spin Hamiltonian parameters, spin S=1/2, C3V symmetry, g//=2.00238 and g⊥=2.00317, central hyperfine interaction (CHF) with one carbon atom and AB//[001]=48G and superhyperfine (SHF) interaction with three equivalent Si neighbour atoms and TB//[001]=12.4G, allow us to attribute the center to a sp3 coordinated carbon dangling bond center, PbC.