The influence of high dielectric constant aluminum oxide sputter deposition on the structure and properties of multilayer epitaxial graphene

Abstract

High dielectric constant aluminum oxide (Al(2)O(3)) is frequently used as the gate oxide in high electron mobility transistors and the impact of its deposition by radio frequency (RF) magnetron sputtering on the structural and electrical properties of multilayer epitaxial graphene (MLG) grown by graphitization of silicon carbide (SiC) is reported. Micro-Raman spectroscopy and temperature dependent Hall mobility measurements reveal that the processing induced changes to the structural and electrical properties of the MLG can be minimal when the oxide deposition conditions are optimal. High-resolution transmission electron microscopy (HRTEM) analysis confirms that the Al(2)O(3)/MLG interface is relatively sharp and that our thickness approximation of the MLG using angle resolved x-ray photoelectron spectroscopy (ARXPS) is accurate. An interface trap density of 5.1 × 10(10) eV(-1) cm(-2) was determined using capacitance-voltage techniques. The totality of our results indicates that ARXPS can be used as a nondestructive tool to measure the thickness of MLG, and that RF sputtered Al(2)O(3) can be used as a high dielectric (high-k) constant gate oxide in multilayer graphene based transistor applications.

Near-edge x-ray absorption fine structure spectroscopy studies of charge redistribution at graphene/dielectric interfaces

“…Chen et al have shown that characteristic Hf-C photoemission peaks observed upon deposition of Hf metal onto graphene by dc sputtering are lost upon subsequent oxidation due to the much higher affinity of hafnium toward oxidation as compared to carbide formation. 31 The broad line shapes likely are a result of inhomogeneous doping, inhomogeneous strain environments, and the introduction of defects. In Fig.…”

Large-Area Electrodeposition of Few-Layer MoS2 on Graphene for 2D Material Heterostructures

“…51 It is worth emphasising that the quality of graphene reported here, which had undergone an electrodeposition process, remains significantly better than those that had undergone a plasma sputtering process from previous reports. [26][27][28][29][30]…”

“…It is worth to emphasise that the quality of graphene reported here, which had undergone an electrodeposition process, remains significantly better than those that had undergone a plasma sputtering process from previous reports. [25][26][27][28][29] X-ray photoelectron spectroscopy (XPS) measurements were performed to study the chemical environments and composition of the Mo and S atoms in the films before and after annealing. Figure 4 shows the Mo 3d (a and c) and S 2p (b and d) region spectra for the exact same area of a sample before and after annealing.…”

“…On the other hand, electrodeposition does not affect its quality as it can be performed at room temperature and pressure. [26][27][28][29][30][31] To the best of our knowledge, the CVD and ALD methods have never demonstrated large scale and continuous film growth of MOS2 over graphene. Limitations of electrodeposition, however, are low crystallinity deposits, the deposition on only conductive materials and the possible incorporation of impurities from the electrolyte.…”

“…24 Furthermore, unlike deposition by plasma sputtering techniques which are carried out in harsh environments that can potentially damage existing materials on the substrate such as graphene, electrodeposition does not affect the quality of the existing materials and can be performed at room temperature and pressure. [25][26][27][28][29] A few works have previously attempted to electrodeposit bulk MoS2 using an aqueous solution over glassy carbon, polytetrafluoroethylene and conductive glass. [30][31][32][33][34] However, building 2D heterostructures for device applications requires that the deposition be done over other 2D materials such as graphene, a common electrical bottom contact material for device structures.…”