Fischetti, Massimo V.
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/2310
An expert in how electrons move in solids, Dr. Fischetti is renowned in the field for the development of DAMOCLES, a computer program that was the first to accurately simulate how electrons move in small semiconductors using what is known as the Monte Carlo transport model. The program is used to design transistors for chips in computers, smartphones and advanced video games.
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Browsing Fischetti, Massimo V. by Subject "Density functionals"
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Item Ab Initio Study of the Electronic Properties and Thermodynamic Stability of Supported and Functionalized Two-Dimensional Sn Films(Amer Physical Soc) Negreira, Ana Suarez; Vandenberghe, William G.; Fischetti, Massimo V.; 0000-0001-5926-0200 (Fischetti, MV); A-4508-2012 (Fischetti, MV)Using density-functional theory (DFT), we study the growth of pristine and functionalized tin monolayers (Sn-MLs) on three different substrates, CdTe, InSb, and Si(111), and the impact these substrates have on the topological insulating properties of the electronic band structure. The presence of the substrate leads to strain and electronic charge transfer, which cause significant changes in the stability and electronic properties of the supported Sn-ML. Growth of pristine Sn-MLs on Si(111) leads to metallic behavior resembling that of the high-buckled Sn-ML phase; pristine Sn-MLs grown on InSb do not maintain a gap throughout the entire Brillouin zone; and pristine Sn-MLs grown on CdTe are unlikely to exhibit an experimentally observable gap. Provided the charge transfer from the substrate can be compensated, halogen-functionalized Sn-MLs grown on CdTe and InSb are topological insulators, albeit with a reduced band gap compared to their free-standing counterparts (from 0.34 eV for Sn-ML-I to 0.17 eV for InSb-Sn-ML-I). We employ ab initio thermodynamics calculations to study the thermodynamic stability of the halogenated InSb-Sn-MLs and CdTe-Sn-MLs surfaces for a temperature range of 100-1000 K under two extreme environments: ultrahigh vacuum (used in most of the laboratory characterization techniques) and rich-halogen conditions (10% vol. halogen environment). Our results indicate that it is possible to obtain stable topologically insulating Sn-MLs grown epitaxially on lattice-matched substrates.Item "Hot Electrons in Si Lose Energy Mostly to Optical Phonons:" Truth or Myth?(American Institute of Physics Inc., 2019-06-05) Fischetti, Massimo V.; Yoder, P. D.; Khatami, Mohammad Mahdi; Gaddemane, Gautam; Van De Put, Maarten L.; 0000-0001-5926-0200 (Fischetti, MV); 0000-0003-0067-8674 (Gaddemane, G); 0000-0001-8014-0350 (Khatami, MM); 0000-0001-9179-6443 (Van de Put, ML); Fischetti, Massimo V.; Khatami, Mohammad Mahdi; Gaddemane, Gautam; Van De Put, Maarten L.Theoretical studies of heat generation and diffusion in Si devices generally assume that hot electrons in Si lose their energy mainly to optical phonons. Here, we briefly review the history of this assumption, and using full-band Monte Carlo simulations - with electron-phonon scattering rates calculated using the rigid-ion approximation and both empirical pseudopotentials and Harris potentials - we show that, instead, electrons lose as much as 2/3 of their energy to acoustic phonons. The scattering rates that we have calculated have been used to study hot-electron effects, such as impact ionization and injection into SiO2, and are in rough agreement with those obtained using density functional theory. Moreover, direct subpicosecond pump-probe experimental results, some of them dating back to 1994, are consistent with the predictions of our model. We conclude that the study of heat generation and dissipation in nanometer-scale Si devices may require a substantial revision of the assumptions that have been considered "common wisdom" so far. © 2019 Author(s).Item Theoretical Studies of Electronic Transport in Monolayer and Bilayer Phosphorene: A Critical Overview(American Physical Society) Gaddemane, Gautam; Vandenberghe, William G.; Van de Put, Maarten L.; Chen, Shanmeng; Tiwari, Sabyasachi; Chen, E.; Fischetti, Massimo V.; 0000-0001-5926-0200 (Fischetti, MV); Gaddemane, Gautam; Vandenberghe, William G.; Van de Put, Maarten L.; Chen, Shanmeng; Tiwari, Sabyasachi; Fischetti, Massimo V.Recent ab initio theoretical calculations of the electrical performance of several two-dimensional materials predict a low-field carrier mobility that spans several orders of magnitude (from 26000 to 35 cm²V⁻¹s⁻¹, for example, for the hole mobility in monolayer phosphorene) depending on the physical approximations used. Given this state of uncertainty, we review critically the physical models employed, considering phosphorene, a group-V material, as a specific example. We argue that the use of the most accurate models results in a calculated performance that is at the disappointing lower end of the predicted range. We also employ first-principles methods to study high-field transport characteristics in monolayer and bilayer phosphorene. For thin multilayer phosphorene we confirm the most disappointing results, with a strongly anisotropic carrier mobility that does not exceed ∼30 cm²V⁻¹s⁻¹ at 300 K for electrons along the armchair direction. We also discuss the dependence of low-field carrier mobility on the thickness of multilayer phosphorene. ©2018 American Physical Society.