Growth and characterization of 3C-SiC grown using CBr4 as a precursor

The growth of silicon carbide on silicon is being studied for many diverse applications and so the search for precursors that could be used to grow with improved or novel physical, structural and morphological properties is a relevant issue in this field. Here we present a study of the use of CBr4 as a precursor in the deposition of 3C-SiC in a cold walled MOVPE reactor. The growth has been studied in a range of temperatures between 1100 and 1250 ?C, on differently oriented substrates. Additionally, the effect of the C:Si ratio in the gas phase was examined by the addition of propane to the reaction mixture. At lower temperatures faceted crystals grew as islands on the substrate; faceting and 2D planar growth was obtained if higher growth temperatures were applied and at higher C:Si ratios. Atomic force and scanning microscopies revealed interesting growth habits of the island type crystals. Transmission electron microscopy in cross-section confirms that these islands are 3C-SiC and have a high crystal perfection. The crystal habit has been characterised and will be presented. Carbon tetrabromide has revealed itself to be a useful precursor for the growth of SiC and, with a judicious control of the growth conditions could be applied to the growth of thin films and nanocrystals

SiC epitaxial growth on Si(100) substrates using carbon tetrabromide

3C-SiC films were grown on Si by VPE using CBr4 as the carbon source, at temperatures ranging from 1100 to 1250?C. XRD, TEM, AFM, and SEM results indicate that the epitaxy proceeds as a 3D growth of uncoalesced islands at low temperature, whereas a continuous layer with hillocks on top is obtained above 1200?C. The shape and faceting of the islands are analyzed by AFM, showing (311) preferred facets.vedi abstract ingles

Van der Waals and Graphene-Like Layers of Silicon Nitride and Aluminum Nitride

A systematic study of kinetics and thermodynamics of Si (111) surface nitridation under ammonia exposure is presented. The appeared silicon nitride (8 × 8) structure is found to be a metastable phase. Experimental evidences of graphene-like nature of the silicon nitride (8 × 8) structure are presented. Interlayer spacings in the (SiN)2(AlN)4 structure on the Si (111) surface are found equal to 3.3 Å in SiN and 2.86 Å in AlN. These interlayer spacings correspond to weak van der Waals interaction between layers. In contrast to the widely accepted model of a surface structure (8 × 8) as monolayer of β-Si3N4 on Si (111) surface, we propose a new graphene-like Si3N4 (g-Si3N3 and/or g-Si3N4) model for the (8 × 8) structure. It is revealed that the deposition of Al atoms on top of a highly ordered (8 × 8) structure results in graphene-like AlN (g-AlN) layers formation. The g-AlN lattice constant of 3.08 Å is found in a good agreement with the ab initio calculations. A transformation of the g-AlN to the bulk-like wurtzite AlN is analyzed

On the Possibility of Realizing a 2D Structure of Si-N Bonds by Metal-Organic Chemical Vapor Deposition

2D SiN honeycomb monolayer structures predicted theoretically have been the focus of interest in materials science for a long time, most recently for their semiconducting and ferromagnetic properties. Herein, by investigating metal-organic chemical vapor deposition processes and direct heat treatment of epitaxial graphene in ammonia flow, the possibility of realizing a certain periodic 2D structure via Si-N bonds under epitaxial graphene on SiC (0001) is reported. The result is of interest because it is compatible with semiconductor material deposition technologies and future use in nanoscience and nanotechnology.Funding Agencies|Swedish Research Council [VR2017-04071, TKP2021-NKTA-05, VEKOP-2.3.3-15-2016-00002, CNR-HAS 2022-25]</p

Nanotechnology for Electronic Materials and Devices

The historical scaling down of electronics devices is no longer the main goal of the International Roadmap for Devices and Systems [...

Nitride layers grown on patterned graphene/SiC

Self-heating of high power GaN devices during their operation is a major drawback that limits the performance. Integration of sheets with very high thermal conductivity material could help in this matter. After some unsuccessful GaN growth experiments carried out directly on graphene, we succeeded to grow nitride layers on patterned graphene/6H-SiC by Metalorganic Chemical Vapour Deposition (MOCVD). The growth is similar to the well-known Epitaxial Lateral Overgrowth method in which the graphene buried stripes are overgrown laterally from the window regions, where AlN could grow on bare SiC with epitaxy. An AlN buffer layer was first deposited on patterned graphene/6H-SiC surface followed by a deposition of ~ 300 nm thick Al0.2Ga0.8N and ~ 1.5 µm thick GaN layer. The AlN buffer deposited onto the graphene stripe was grown in a 3D way (Fig.1a). The heterostructure was studied using aberration-corrected transmission electron microscopy (TEM) methods in combination of electron energy-loss X-ray spectroscopy (EDXS) and electron energy-loss spectroscopy (EELS). TEM specimens were prepared using both conventional and focused ion beam methods.The most surprising details of this study is the appearance of the AlN/GaN superlattices, which were formed in a self-organised way over the buffer layer. Instead the ternary AlGaN we have superlattice (Fig. 1.b and c) in which the thickness of the AlN/GaN is determined by the available elements from the Al0.2Ga0.8N which we wanted to grow. The control sample (without graphene) showed a much more flat AlN buffer and a ternary Al0.2Ga0.8N on that without any phase separation. EDXS mapping and also superlattice reflections show however, clearly the complete phase separation in the case the nitride layers are grown on graphene. We suppose, that some excess carbon induced the phase separation.The detailed TEM studies revealed the AlN nucleation directly on SiC and lateral overgrowth of graphene island as shown in Fig.2a. The high resolution image in Fig.2.b shows three layers of graphene and the AlN that is in epitaxy with SiC. Both interfaces are sharp and no interdiffusion of the elements are observed according to the Si, C (not shown) and Al maps in Fig. 2c The results show that high quality GaN layer over graphene/SiC can be grown with MOCVD that can serve as templates for high power GaN devices

2D graphitic-like gallium nitride and other structural selectivity in confinement at the graphene/SiC interface

Beyond the predictions routinely achievable by first-principles calculations and using metal-organic chemical vapor deposition (MOCVD), we report a GaN monolayer in a buckled geometry obtained in confinement at the graphene/SiC interface. Conductive atomic force microscopy (C-AFM) was used to investigate vertical current injection across the graphene/SiC interface and to establish the uniformity of the intercalated regions. Scanning transmission electron microscopy (S/TEM) was used for atomic resolution imaging and spectroscopy along the growth direction. The experimentally obtained value of the buckling parameter, 1.01 &amp; PLUSMN; 0.11 &amp; ANGS;, adds to the existing knowledge of buckled GaN monolayers, which is based solely on predictive first-principles calculations. Our study reveals a discontinuity in the anticipated stacking sequence attributed to a few-layer graphitic-like GaN structure. Instead, we identify an atomic order suggestive of ultrathin gallium oxide Ga2O3, whose formation is apparently mediated by dissociative adsorption of oxygen onto the GaN monolayer. An atomic resolution image of an intercalated structure at a graphene/SiC interface along the growth direction which is determined as a buckled GaN monolayer at the immediate interface with an underlying SiC substrate and ultrathin Ga2O3 on top.Funding Agencies|Swedish Research Council (VR) [VR 2017-04071, VR 2015-06816]; European Structural and Investment Funds [TKP2021-NKTA-05, VEKOP-2.3.3-15-2016-00002]; GHOST III bilateral project [CNR-HAS 2023-2025]; Italian Ministry of Education and Research (MIUR) [PON a3_00363]; European Union [823717]</p

Indium Nitride at the 2D Limit

The properties of 2D InN are predicted to substantially differ from the bulk crystal. The predicted appealing properties relate to strong in- and out-of-plane excitons, high electron mobility, efficient strain engineering of their electronic and optical properties, and strong application potential in gas sensing. Until now, the realization of 2D InN remained elusive. In this work, the formation of 2D InN and measurements of its bandgap are reported. Bilayer InN is formed between graphene and SiC by an intercalation process in metal-organic chemical vapor deposition (MOCVD). The thickness uniformity of the intercalated structure is investigated by conductive atomic force microscopy (C-AFM) and the structural properties by atomic resolution transmission electron microscopy (TEM). The coverage of the SiC surface is very high, above 90%, and a major part of the intercalated structure is represented by two sub-layers of indium (In) bonded to nitrogen (N). Scanning tunneling spectroscopy (STS) measurements give a bandgap value of 2 +/- 0.1 eV for the 2D InN. The stabilization of 2D InN with a pragmatic wide bandgap and high lateral uniformity of intercalation is demonstrated.Funding Agencies|FLAG-ERA 2015 JTC project GRIFONE through Swedish Research Council [VR 2015-06816]; National Research Development and Innovation Office, Hungary NN [118914]; FLAG-ERA 2015 JTC project GRIFONE through Swedish Research Council VR [2015-06816]; National Research Development and Innovation Office, Hungary [NN 118914]; Italian Ministry of Education and Research (MIUR) under project Beyond-NanoMinistry of Education, Universities and Research (MIUR) [PON a3_00363]; Italian Ministry of Education and Research (MIUR)Ministry of Education, Universities and Research (MIUR) [PON ARS01_01007]; European Structural and Investment Funds [VEKOP-2.3.3-15-2016-00002]; European Unions Horizon 2020 research and innovation programme [823717 - ESTEEM3]; [VR 2017-04071]; [KAW 2013.0049]</p

Material proposal for 2D indium oxide

Realization of semiconductor materials at the two-dimensional (2D) limit can elicit exceptional and diversified performance exercising transformative influence on modern technology. We report experimental evidence for the formation of conceptually new 2D indium oxide (InO) and its material characteristics. The formation of 2D InO was harvested through targeted intercalation of indium (In) atoms and deposition kinetics at graphene/SiC interface using a robust metal organic chemical vapor deposition (MOCVD) process. A distinct structural configuration of two sub-layers of In atoms in "atop" positions was imaged by scanning transmission electron microscopy (STEM). The bonding of oxygen atoms to indium atoms was indicated using electron energy loss spectroscopy (EELS). A wide bandgap energy measuring a value of 4.1 eV was estimated by conductive atomic force microscopy measurements (C-AFM) for the 2D InO.Funding Agencies|FLAG-ERA 2015 JTC project GRIFONE through Swedish Research Council [VR 2015-06816]; National Research Development and Innovation Office, Hungary [NN 118914]; Italian Ministry of Education and Research (MIUR) under the project EleGaNTeMinistry of Education, Universities and Research (MIUR) [PON ARS01_01007]; European Structural and Investment Funds [VEKOP-2.3.3-15-2016-00002]; Swedish Foundation for Strategic Research (SSF)Swedish Foundation for Strategic Research [RIF 14-0074]; Knut and Alice Wallenbergs FoundationKnut &amp; Alice Wallenberg Foundation; [VR 2017-04071]</p