3C-SiC Thin Films Research Articles

Epitaxial graphene on single domain 3C-SiC(100) thin films grown on off-axis Si(100)

The current process of growing graphene by thermal decomposition of 3C-SiC(100) on silicon is technologically attractive. Here, we study epitaxial graphene on single domain 3C-SiC films on off-axis Si(100). The structural and electronic properties of such graphene layers are explored by atomic force microscopy, x-ray photoelectron spectroscopy, and Raman spectroscopy. Using low energy electron diffraction, we show that graphene exhibits single planar domains. Near-edge x-ray absorption fine structure is used to characterize the sample, which confirms that the graphene layers present sp2 hybridization and are homogeneously parallel to the substrate surface.

Tensile mechanical behaviors of cubic silicon carbide thin films

Molecular dynamics (MD) methods using Tersoff potential are employed to study the nanomechanical behaviors of 3C-SiC (010) thin films under [100]-oriented tension. In this work, the Young’s modulus, tensile strength and elongation of thin films are compared with those of the bulk 3C-SiC for different temperatures. The results show that Young’s modulus of the nanofilms is size dependent and softer than its bulk counterpart. It is found that Young’s modulus decreases as much as 24.7% when the thickness of the thin film reduces to unit lattice, which suggests that size effect could not be neglected when the characteristic length shrinks down to several nanometers. When the thickness of the thin films is more than 10nm, and thin film value converges to the bulk value. As the increment of thin film value is very slow, the size effects of 3C-SiC could be neglected. In addition, the reduction in Young’s modulus of the nanofilm with increasing temperature exhibits a nonlinear trend. Moreover, the simulations demonstrate that the tensile strength and elongation of bulk 3C-SiC also decreases with the increase of temperature. Despite partial degradation, SiC nanofilm maintains its mechanical properties largely at elevated temperatures, which makes it attractive for applications in high temperature environment.

Epitaxy of Graphene on 3C-SiC(111) Thin Films on Microfabricated Si(111) Substrates

The epitaxy of graphene on 3C-SiC(111) formed on microfabricated Si(111) has been demonstrated. Through observations by optical microscopy, micro-Raman spectroscopy, low-energy electron diffraction, and photoelectron spectroscopy, it has been confirmed that the epitaxial graphene is Bernal-stacked with a buffer layer present between graphene and the 3C-SiC film, which can lead to the opening of the band gap necessary for logic operations. The quality of graphene is improved by the shrinkage of the pattern. These results indicate that graphene on silicon using the microfabricated substrate is a promising material for the realization of graphene-based devices.

Epitaxy of Graphene on 3C-SiC(111) Thin Films on Microfabricated Si(111) Substrates

The epitaxy of graphene on 3C-SiC(111) formed on microfabricated Si(111) has been demonstrated. Through observations by optical microscopy, micro-Raman spectroscopy, low-energy electron diffraction, and photoelectron spectroscopy, it has been confirmed that the epitaxial graphene is Bernal-stacked with a buffer layer present between graphene and the 3C-SiC film, which can lead to the opening of the band gap necessary for logic operations. The quality of graphene is improved by the shrinkage of the pattern. These results indicate that graphene on silicon using the microfabricated substrate is a promising material for the realization of graphene-based devices.

Improvement in Film Quality of Epitaxial Graphene on SiC(111)/Si(111) by SiH4 Pretreatment

The epitaxy of graphene on 3C-SiC/Si (GOS) has attracted much attention owing to its viability to fuse graphene with Si-based technologies. It is known that the surface condition of the 3C-SiC thin film before graphitization plays a decisive role in determining the quality of the GOS film. We have investigated the effect of the pretreatment of the 3C-SiC thin film in vacuo at a SiH4 partial pressure of 6.7 ×10-4 Pa on the subsequent formation of graphene. As a result, it is revealed that the SiH4 pretreatment restores the defects on the SiC surface, such as the Si vacancy and point defects formed by the presence of native oxides, and improves the quality of graphene. The effect is found to be highest when the substrate temperature is 1173 K.

Seebeck Coefficient of Heavily Doped Polycrystalline 3C-SiC Deposited by LPCVD

The Seebeck coefficient of heavily-nitrogen-doped n-type polycrystalline 3C-SiC (n-SiC) and platinum (Pt) thin films has been measured from room temperature up to 300 °C by using a microfabricated test structure. At room temperature, the absolute Seebeck coefficient of the n-SiC is -10 μV/°C. With ambient temperature increase, the absolute Seebeck coefficient of the n-SiC is found to gradually increase, reaching -20 μV/°C at 300 °C.

Fabrication and characterization of surface type Schottky diode hydrogen sensor using polyaniline/porous 3C-SiC

This paper describes the fabrication and characterization of a hydrogen sensor that uses polyaniline (PANI) nanofiber/porous 3C-SiC (PSiC) heterojunctions. In this work, a PSiC with pore diameter of 50nm was formed from polycrystalline N-type 3C-SiC thin films by electrochemical anodization. PANI nanofibers with an average diameter of 60nm and length of 300nm were synthesized in compressed liquid carbon dioxide on PSiC, using the 2-step spin coating method. The electrical characteristics of PANI on PSiC heterojunction diodes were evaluated with current voltage measurements, showing a P–N junction. Hydrogen sensing properties were investigated at various temperatures with H2 concentrations ranging from 30ppm to 150ppm. The response decreased as the temperature increased. However, a high linearity response was shown at 100°C with H2 concentrations. The response and recovery time was decreased at temperatures below 125°C and unstable sensing properties were shown at 150°C. The best performance was observed at 100°C, with fast response and fast recovery times of 10 and 6s, respectively.

Effects of In-situ Doping on the Electrical and the Optical Characteristics of Anodized Polycrystalline 3C-SiC Thin Films Fabricated Using Chemical Vapor Deposition with a Single Precursor of Hexamethyldisilane

Effects of In-situ Doping on the Electrical and the Optical Characteristics of Anodized Polycrystalline 3C-SiC Thin Films Fabricated Using Chemical Vapor Deposition with a Single Precursor of Hexamethyldisilane

Characteristics of Anodized Polycrystalline 3C-SiC Thin Films Deposited by Using Chemical Vapor Deposition with Single-precursor Hexamethyldisilane for Different In-situ-doping Concentrations

Characteristics of Anodized Polycrystalline 3C-SiC Thin Films Deposited by Using Chemical Vapor Deposition with Single-precursor Hexamethyldisilane for Different In-situ-doping Concentrations

Low-Energy-Electron-Diffraction and X-ray-Phototelectron-Spectroscopy Studies of Graphitization of 3C-SiC(111) Thin Film on Si(111) Substrate

Low-Energy-Electron-Diffraction and X-ray-Phototelectron-Spectroscopy Studies of Graphitization of 3C-SiC(111) Thin Film on Si(111) Substrate

Low-Energy-Electron-Diffraction and X-ray-Phototelectron-Spectroscopy Studies of Graphitization of 3C-SiC(111) Thin Film on Si(111) Substrate

Epitaxial graphene can be formed on silicon substrates by annealing a 3C-SiC film formed on a silicon substrate in ultrahigh vacuum (G/3C-SiC/Si). In this work, we explore the graphitization process on the 3C-SiC(111)/Si(111) surface by using low-energy electron diffraction and X-ray photoelectron spectroscopy (XPS) and compare them with that on 6H-SiC(0001). Upon annealing at T≥1150 °C, the 3C-SiC(111)/Si(111) surface follows the sequence of (√3×√3)R30°, (6√3×6√3)R30°, and (1×1)graphene in the surface structures. The C 1s core level according to XPS indicates that a buffer layer, identical with that in G/6H-SiC(0001), exists at the G/3C-SiC(111) buffer. These observations strongly suggest that graphitization on the surface of the 3C-SiC(111) face proceeds in a similar manner to that on the Si-terminated hexagonal bulk SiC crystals.

Multi-wafer 3C-SiC thin films grown on Si (100) in a vertical HWLPCVD reactor

We report the latest results of the 3C-SiC layer growth on Si (100) substrates by employing a novel home-made horizontal hot wall low pressure chemical vapour deposition (HWLPCVD) system with a rotating susceptor that was designed to support up to three 50 mm-diameter wafers. 3C-SiC film properties of the intra-wafer and the wafer-to-wafer, including crystalline morphologies and electronics, are characterized systematically. Intra-wafer layer thickness and sheet resistance uniformity (σ/mean) of ∼3.40% and ∼5.37% have been achieved in the 3 × 50 mm configuration. Within a run, the deviations of wafer-to-wafer thickness and sheet resistance are less than 4% and 4.24%, respectively.

Transmission Electron Microscopy and Raman-Scattering Spectroscopy Observation on the Interface Structure of Graphene Formed on Si Substrates with Various Orientations

Graphene can be grown on three major low-index substrates of Si(111), (110), and (001) by forming a 3C-SiC thin film and by subliming Si atoms from the top few layers of the SiC film. We have investigated the structure of graphene/3C-SiC interface by cross-sectional transmission electron microscopy (XTEM) and Raman-scattering spectroscopy. While the interface layer quite similar to that on the graphene/6H-SiC(0001) face is found to exist on the 3C-SiC(111)/Si(111) substrate, no such interface structure exists on the (110)- and (001)-oriented faces.

Analytical Model of Stress Relaxation in 3C SiC Layers on Silicon

In this work we analyze the static behavior of cantilevers elaborated on the basis of 3C SiC thin films grown by chemical vapor deposition on (100) and (111) oriented silicon substrates. A direct microscope observation of cantilever bending indicates the opposite sign of stress gradient (respectively negative and positive) for both film orientations. The correlation of this observation with the commonly admitted nature of intrinsic stress for each orientation (respectively compressive and tensile) leads us to an unexpected conclusion: instead of relaxing, the absolute value of the intrinsic stress increases from the interface to the layer surface. We propose an analytical model that could explain this phenomenon.

Relaxation of a strained 3C-SiC(1 1 1) thin film on silicon by He + and O + ion beam defect engineering

In this paper we report on the successful reduction of tensile strain in a thin strained ion-beam synthesized 3C-SiC(1 1 1) layer on silicon. The creation of a near-interface defect structure consisting of nanometric voids and stacking fault type defects by He ion implantation and subsequent annealing yields significant relaxation in the top SiC film. The microstructure of the defect layer is studied by transmission electron microscopy, and the strain state of the 3C-SiC layer was studied by high-resolution X-ray diffraction in a parallel beam configuration. Typical process conditions for the growth of GaN films on the SiC layer were emulated by high temperature treatments in a rapid thermal annealer or a quartz tube furnace. It is found that prolonged annealing at high temperatures leads to ripening of the voids and to a weaker reduction of the tensile strain. It is shown that this problem can be overcome by the co-implantation of oxygen ions to form highly thermally stable void/extended defect structures.

여러 탄화조건에 따라 성장된 단결정 3C-SiC 박막의 특성

This paper describes the crystallinity, growth rate, and surface morphology of single crystalline 3C-SiC (cubic silicon carbide) thin films grown with several carbonization conditions such as temperature, flow rate, time. In case of carbonization, an increase in the carbonization temperature caused a increase in the size and numbers of unsealed void (big black spot) which decrease the crystallinity. In addition, optimal flow rate made carbonization layer form well and prevented the formation of voids. Also, after a period of time, the growth of carbonization layer did not increase no more. The single crystalline 3C-SiC thin films on optimal carbonized Si substrate showed an improvement on the crystallinity, the growth rate, the roughness, and the carrier concentration.

(Invited) Epitaxial Formation of Graphene on Si Substrates: From Heteroepitaxy of 3C-SiC to Si Sublimation

Epitaxial graphene can be formed on Si substrates by a vacuum annealing of a 3C-SiC thin film preformed on Si substrate. In this graphene-on-silicon (GOS) method, graphene grows on three major low-index planes of Si substrates: Si(111), (110), and (100). Despite the difference in the quality of the SiC film depending on the orientation, the quality of the formed graphene shows very little variation, leaving the growth mechanism of graphene on cubic SiC crystals open to future studies. The growth rate of graphene, however, shows a sharp dependence on the orientation, which increases in the order of (111) < (001) < (110).

Surface Chemistry Involved in Epitaxy of Graphene on 3C-SiC(111)/Si(111)

Surface chemistry involved in the epitaxy of graphene by sublimating Si atoms from the surface of epitaxial 3C-SiC(111) thin films on Si(111) has been studied. The change in the surface composition during graphene epitaxy is monitored by in situ temperature-programmed desorption spectroscopy using deuterium as a probe (D2-TPD) and complementarily by ex situ Raman and C1s core-level spectroscopies. The surface of the 3C-SiC(111)/Si(111) is Si-terminated before the graphitization, and it becomes C-terminated via the formation of C-rich (6√3 × 6√3)R30° reconstruction as the graphitization proceeds, in a similar manner as the epitaxy of graphene on Si-terminated 6H-SiC(0001) proceeds.

Electrical characterization of Au/3C-SiC/ n-Si/Al Schottky junction

High temperature silicon carbide Schottky diode was fabricated with Au deposited on poly 3C-SiC thin film grown on n-type Si(1 0 0) using atmospheric pressure chemical vapor deposition. The charge transport mechanism of the diode was studied in the temperature range of 300–550 K. The forward and reverse bias currents of the diode increase strongly with temperature and the diode shows a non-ideal behavior due to the series resistance and the interface states associated with 3C-SiC. The charge transport mechanism is a temperature activated process, in which, the electrons passes over of the low barriers and in turn, the diode has a large ideality factor. The electrical parameters of the Au/3C-SiC/ n-Si/Al Schottky diode were explained on the basis of the thermionic emission theory with double Gaussian distribution of the barrier heights due to the barrier height inhomogeneities at metal/semiconductor interface. The interface state density of the diode was determined by the conductance–frequency method and it was of order of 9.18 × 10 10 eV −1 cm −2.

Micro-Raman Mapping of 3C-SiC Thin Films Grown by Solid-Gas Phase Epitaxy on Si (111).

A series of 3C-SiC films have been grown by a novel method of solid–gas phase epitaxy and studied by Raman scattering and scanning electron microscopy (SEM). It is shown that during the epitaxial growth in an atmosphere of CO, 3C-SiC films of high crystalline quality, with a thickness of 20 nm up to few hundreds nanometers can be formed on a (111) Si wafer, with a simultaneous growth of voids in the silicon substrate under the SiC film. The presence of these voids has been confirmed by SEM and micro-Raman line-mapping experiments. A significant enhancement of the Raman signal was observed in SiC films grown above the voids, and the mechanisms responsible for this enhancement are discussed.