Thierry Chassagne

Epitaxial graphene on cubic SiC(111)/Si(111) substrate

Epitaxial graphene films grown on silicon carbide (SiC) substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of epitaxial graphene films on 3C-SiC(111)Si(111) substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer graphene (FLG) surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.

Comparative study of the role of the nucleation stage on the final crystalline quality of (111) and (100) silicon carbide films deposited on silicon substrates.

We study the impact of the nucleation step on the final crystalline quality of 3C-SiC heteroepitaxial films grown on (111) and (100) oriented silicon substrates by low pressure chemical vapor deposition. The evolution of both the structural and morphological properties of 3C-SiC epilayers in dependence on the only nucleation parameters (propane flow rate and duration of the process) are investigated by means of x-ray diffraction, scanning electron, atomic force, and optical microscopies. At first, we show how the formation of interfacial voids is controlled by the experimental parameters, as previously reported, and we correlate the density of voids with the substrate sealing by using an analytical model developed by V. Cimalla et al. [Mater. Sci. Eng., B 46, 190 (1997)]. We show that the nucleation stage produces a more dense buffer layer in case of (111) substrates. Further, we investigate the impact of the nucleation parameters on the crystalline quality of 3C-SiC epilayers. Within our experimental set...

Direct growth of few-layer graphene on 6H-SiC and 3C-SiC/Si via propane chemical vapor deposition

We propose to grow graphene on SiC by a direct carbon feeding through propane flow in a chemical vapor deposition reactor. X-ray photoemission and low energy electron diffraction show that propane allows to grow few-layer graphene (FLG) on 6H-SiC(0001). Surprisingly, FLG grown on (0001) face presents a rotational disorder similar to that observed for FLG obtained by annealing on (000–1) face. Thanks to a reduced growth temperature with respect to the classical SiC annealing method, we have also grown FLG/3C-SiC/Si(111) in a single growth sequence. This opens the way for large-scale production of graphene-based devices on silicon substrate.

Evidence of electrical activity of extended defects in 3C-SiC grown on Si

In this paper, we demonstrate the high electrical activity of extended defects found in 3C–SiC heteroepitaxially grown layer on (100) silicon substrates. Cross-sectional scanning transmission electron microscopy analysis was performed to reveal the defects while scanning spreading resistance microscopy aimed to study their electrical behavior. Using this technique, complete layer resistance cartography was done. The electrical activity of the extended defects in 3C–SiC was clearly evidenced. Furthermore, the defect activity was estimated to be higher than that of heavily nitrogen doped (5×1018 cm−3) 3C–SiC layer.

Stress relaxation during the growth of 3C-SiC∕Si thin films

In this work the authors study the strain of 3C-SiC thin films grown on (001) on-axis silicon substrates. They use ex situ wafer curvature measurements to monitor the residual strain of silicon carbide film. At high temperature creep effects take place and modify the intrinsic strain of silicon carbide film. From the time and temperature dependences of these effects, they determine the creep exponent and the creep activation energy for 3C-SiC. Obtained values of N=2.6±0.3 and Q=5.6±1.0eV are similar to those reported in literature for hexagonal polytypes of silicon carbide.

Quantum Hall resistance standards from graphene grown by chemical vapour deposition on silicon carbide

Replacing GaAs by graphene to realize more practical quantum Hall resistance standards (QHRS), accurate to within 10−9 in relative value, but operating at lower magnetic fields than 10 T, is an ongoing goal in metrology. To date, the required accuracy has been reported, only few times, in graphene grown on SiC by Si sublimation, under higher magnetic fields. Here, we report on a graphene device grown by chemical vapour deposition on SiC, which demonstrates such accuracies of the Hall resistance from 10 T up to 19 T at 1.4 K. This is explained by a quantum Hall effect with low dissipation, resulting from strongly localized bulk states at the magnetic length scale, over a wide magnetic field range. Our results show that graphene-based QHRS can replace their GaAs counterparts by operating in as-convenient cryomagnetic conditions, but over an extended magnetic field range. They rely on a promising hybrid and scalable growth method and a fabrication process achieving low-electron-density devices.

Investigation of 2 inch SiC layers grown in a resistively-heated LP-CVD reactor with horizontal “hot-walls”

With respect to more standard and more widely used inductive-heating, the resistivelyheated reactors offer the strong advantage of low cost, easy installation and low running constraints. Combined with an easy adaptation to the increasing size of wafers, this results in very strong advantages. This simple technique was mainly restricted to the growth of small size samples for academic purpose [1]. In this work we report an investigation of 2 inch SiC layers deposited in a new, horizontal and resistively-heated, “hot-wall” LP-CVD reactor specially designed for large flexibility. Introduction Due to superior physical properties, SiC appears as a most promising material for high power, high frequency and high temperature electronic devices or sensors. In this case, whatever is the targeted application, one needs to deposit a low doped, electronic grade material, on a large diameter single crystalline wafer. A promising technique is the use of hot-wall CVD, coupled with resistive heaters. With respect to the more standard and widely used inductive-heating technology, a resistivelyheated reactor offers advantages in terms of (low) cost, (easy) installation and (low) running constraints. Combined with a very easy adaptation to the increasing size of wafers, this seems very appealing. Unfortunately, up to now, this simple technique has been restricted to the growth of small size samples for academic purpose [1] and was not seriously considered for industrial applications. In order to establish more the potentiality of this system, we report a detailed investigation of the thickness uniformity, surface morphology and low temperature photoluminescence properties of a series of epitaxial layers deposited on silicon. We show that, on 2” Si substrates, state of the art material can be easily obtained. Experimental The reactor has been specially designed to allow, both, usual SiC growth by LP-CVD [1] as well as full Si-wafer conversion by LPE [2]. In this case, the control of the vertical temperature gradient is essential to insure an optimised liquid phase diffusion. This technical constraint dictated the choice of two independent heaters (upper and lower resistive) forming then a standard“hot-walls” configuration. The walls are thin (0.5mm) and made of high purity graphite sheets. The thermal inertia is then very low, which allows RTP (Rapid Thermal Processing) to be done up to 1800°C. In order to Materials Science Forum Online: 2004-06-15 ISSN: 1662-9752, Vols. 457-460, pp 273-276 doi:10.4028/www.scientific.net/MSF.457-460.273

A comprehensive study of SiC growth processes in a VPE reactor

Abstract We performed an experimental study of the effect of the gas phase composition on the growth mechanism of 3C-SiC on Si(100) by atmospheric-pressure vapour phase epitaxy at 1350°C. Silane and propane diluted in hydrogen were used as precursors for the growth. We demonstrate the existence of an equilibrium partial pressure of carbon above the growing surface, which ensures a mirror-like morphology. For too low a carbon partial pressure (C/Si ratio in the gas phase lower than 2.7 with a growth rate of 3 μm h −1 ), the layer morphology and crystalline quality quickly degrade. For too high a carbon partial pressure (C/Si ratio higher than 5 with the same growth rate), SiC clusters form on the growing layers. We propose a mechanism of formation for these clusters taking into account the interactions between the C and Si species in the hot boundary layer.

Effects of pressure, temperature, and hydrogen during graphene growth on SiC(0001) using propane-hydrogen chemical vapor deposition

Graphene growth from a propane flow in a hydrogen environment (propane-hydrogen chemical vapor deposition (CVD)) on SiC differentiates from other growth methods in that it offers the possibility to obtain various graphene structures on the Si-face depending on growth conditions. The different structures include the (6√3 × 6√3)-R30° reconstruction of the graphene/SiC interface, which is commonly observed on the Si-face, but also the rotational disorder which is generally observed on the C-face. In this work, growth mechanisms leading to the formation of the different structures are studied and discussed. For that purpose, we have grown graphene on SiC(0001) (Si-face) using propane-hydrogen CVD at various pressure and temperature and studied these samples extensively by means of low energy electron diffraction and atomic force microscopy. Pressure and temperature conditions leading to the formation of the different structures are identified and plotted in a pressure-temperature diagram. This diagram, togeth...

Transmission electron microscopy investigation of microtwins and double positioning domains in (111) 3C-SiC in relation with the carbonization conditions

In this work, transmission electron microscopy is used to investigate the influence of the carbonization conditions on the formation of crystal defects in 3C-SiC layers deposited on (111) silicon. We focus on two kinds of defects; (1) the stacking faults and microtwins lying in the (1¯1¯1) planes, and (2) the double positioning domains. While the density of the stacking faults and microtwins is found independent on the carbonization conditions, the size of the double positioning domains is strongly influenced by the propane flow rate and can be related to the substrate sealing at the early stage of carbonization.