AVS 68 Session EM+AS+EL+NS+SS-ThA: Interfaces and Defect Engineering in Electronic & Photonic Materials & Devices

Thursday, November 10, 2022 2:20 PM in Room 304

Thursday Afternoon

Session Abstract Book
(251KB, Nov 18, 2022)
Time Period ThA Sessions | Abstract Timeline | Topic EM Sessions | Time Periods | Topics | AVS 68 Schedule

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2:20 PM EM+AS+EL+NS+SS-ThA-1 Design and Control of Defect-Mediated Properties in Electronic Ceramics
Elizabeth Dickey (Carnegie Mellon University)

Crystalline lattice defects, e.g. vacancies, interstitials or substitutional ions, play an important role in the conductivity and dielectric properties of electronic ceramics. The material “defect chemistry” can be tuned to optimize the electronic and ionic conductivities for particular applications via doping, oxygen-activity and temperature control during processing. Beyond controlling the majority defect (carrier) concentrations, it is also important to control the minority defect concentrations as these can be especially relevant to the time-dependent electrical behavior. For example, applied electric fields in device applications provide a strong driving force for the electromigration of charged lattice defects. Furthermore, external conditions such as humidity, which can lead to proton incorporation, can also strongly influence time-dependent material properties. This talk will review our current understanding and implications of point defect equilibria, partial equilibria and dynamics in several prototypical electronic ceramics. Recent efforts to effectively co-dope dielectric materials to improve simultaneously limit both the electronic and ionic conductivity will be discussed.

3:00 PM EM+AS+EL+NS+SS-ThA-3 In-Situ Investigation of the Interface Formation between Si-Terminated Diamond and a NbxOy Electron Acceptor Layer for Electronic Applications
Gabrielle Abad, Patrick Hopkins, Stephen McDonnell (University of Virginia)

Ultra-wide band gap semiconductors present one avenue for the next generation of semiconductor devices. Diamond, specifically, has shown promise in high power, frequency, and temperature electronics; however, issues with impurity doping has limited the development of diamond-based devices. Instead, surface charge transfer doping (SCTD), which avoids introduction of foreign atoms into the diamond lattice, has been used for inducing a two-dimensional hole gas at the diamond surface thus increasing its conductivity. The established method to achieve SCTD is to hydrogen-terminate the diamond surface prior to the addition of an electron acceptor layer; however, the degree of SCTD induced by H-termination is largely dependent on atmospheric exposure. Alternatively, silicon-termination of the diamond surface has been shown to produce the ordered surface with the negative electron affinity necessary for the SCTD mechanism. In this work, we investigate the combination of Si-terminated diamond with a NbxOy electron acceptor layer, wherein we focus on understanding interface formation and chemistries, as well as elucidating if the band alignment mechanism is responsible for SCTD for this material system. Ultra-high vacuum (UHV) electron beam (e-beam) deposition of Si onto diamond substrates was carried out, followed by UHV annealing to produce the Si-terminated (100) diamond surface. X-ray photoemission spectroscopy (XPS) of core-level and valence band spectra was used to analyze chemical composition. To form the electron acceptor layer, Nb films were e-beam deposited onto the Si-terminated diamond surface by depositing Nb under varying oxygen partial pressures. XPS was used to observe how interfacial chemistry, electronic structure, and band alignment evolve with different NbxOy compositions. The air stability of the electron acceptor layers was also investigated after atmospheric exposure via XPS. Analysis of the valence band spectra shows that band alignment would not result in SCTD for the NbxOy/Si/diamond material system.

3:20 PM EM+AS+EL+NS+SS-ThA-4 Effects of Atmospheric UV-O3 Exposure of WSe2 on the Properties of the HfO2/WSe2 Interface
Maria Gabriela Sales (University of Virginia); Alexander Mazzoni (University of Maryland College Park); Wendy Sarney (Army Research Laboratory); Justin Pearson (University of Maryland College Park); Sina Najmaei (Army Research Laboratory); Stephen McDonnell (University of Virginia)
Transition metal dichalcogenides (TMDCs) are a class of two-dimensional (2D) layered materials, in which each layer is held in-plane by strong chemical bonds, but held in the out-of-plane direction by weak van der Waals forces. For integration in an electronic device, TMDCs are typically capped in the gate region with a high-quality dielectric layer, where ultrathin (sub-5 nm) dielectric thicknesses are desired in order to achieve sufficient gate to channel electrostatic coupling. The unreactive basal plane of TMDCs makes atomic layer deposition (ALD) of dielectric films directly on top of these 2D materials challenging. In this work, we investigate the effects of atmospheric ultraviolet-ozone (UV-O3) exposures of WSe2 and use the UV-O3 functionalized WSe2 surfaces as substrates for ALD of HfO2. We report two UV-O3 functionalization regimes observed on WSe2: lower exposure times, which do not result in oxidation of the WSe2 surface, and higher exposure times, which result in a tungsten oxyselenide top layer. The properties of this oxidized layer, such as its thickness, structure, air stability, and thermal stability, are also investigated. Additionally, we note that both functionalization regimes result in variably doped WSe2. We report on the interface chemistry observed after subsequent ALD of HfO2, as measured with X-ray photoelectron spectroscopy (XPS). We note that variable, depth-sensitive doping states are found in the WSe2 functionalized with higher exposure times. We also study the resultant morphologies of our deposited HfO2 films with atomic force microscopy (AFM), and we find that both of our UV-O3 functionalization regimes result in uniform and smooth HfO2 films directly deposited by ALD. With the different functionalization regimes (with different interface chemistries) all providing uniform dielectric film deposition, our atmospheric UV-O3 exposure technique on WSe2 presents unique tunability and flexibility in the design of interfaces in devices.
3:40 PM EM+AS+EL+NS+SS-ThA-5 Near Zero Field Magnetoresistance and Electrically Detected Magnetic Resonance Studies of Instabilities in Semiconductor/ Insulator Systems
Patrick Lenahan (Pennsylvania State University)

We have utilized both electrically detected magnetic resonance(EDMR) and near zero field magnetoresistance (NZFMR) spectroscopy to investigate the physics involved in instabilities such as stress induced leakage currents and time dependent dielectric breakdown in Si/SiO2 and SiC/ SiO2 systems. Both techniques are extremely sensitive and extend the sensitivity of conventional electron spin based techniques down to near nanoscale device structures. We find that the very simple spin-based NZFMR technique has significant analytical power in these investigations. The NZFMR studies can complement the more established EDMR measurements with simple and relatively inexpensive apparatus.

Session Abstract Book
(251KB, Nov 18, 2022)
Time Period ThA Sessions | Abstract Timeline | Topic EM Sessions | Time Periods | Topics | AVS 68 Schedule