materials Review Diamond for Electronics: Materials, Processing and Devices Daniel Araujo 1, *, Mariko Suzuki 1 , Fernando Lloret 2 , Gonzalo Alba 1 and Pilar Villar 1   Citation: Araujo, D.; Suzuki, M.; Lloret, F.; Alba, G.; Villar, P. Diamond for Electronics: Materials, Processing and Devices. Materials 2021, 14, 7081. https://doi.org/10.3390/ma14227081 Academic Editor: Fabrizio Roccaforte Received: 29 August 2021 Accepted: 8 November 2021 Published: 22 November 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Materials Science and Engineering, University of Cádiz, 11510 Puerto Real, Spain; mariko.suzuki@uca.es (M.S.); gonzalo.alba@uca.es (G.A.); pilar.villar@uca.es (P.V.) 2 Department of Applied Physics, University of Cádiz, 11510 Puerto Real, Spain; fernando.lloret@uca.es * Correspondence: daniel.araujo@uca.es Abstract: Progress in power electronic devices is currently accepted through the use of wide bandgap materials (WBG). Among them, diamond is the material with the most promising characteristics in terms of breakdown voltage, on-resistance, thermal conductance, or carrier mobility. However, it is also the one with the greatest difficulties in carrying out the device technology as a result of its very high mechanical hardness and smaller size of substrates. As a result, diamond is still not considered a reference material for power electronic devices despite its superior Baliga’s figure of merit with respect to other WBG materials. This review paper will give a brief overview of some scientific and technological aspects related to the current state of the main diamond technology aspects. It will report the recent key issues related to crystal growth, characterization techniques, and, in particular, the importance of surface states aspects, fabrication processes, and device fabrication. Finally, the advantages and disadvantages of diamond devices with respect to other WBG materials are also discussed. Keywords: diamond; MPCVD growth; power electronics; electron microscopy 1. Motivations In the 2020 and 2030 Climate-Energy Packages, the EU committed to lower greenhouse gas emissions by 20% with respect to 1990 and 55% by 2030 (very recent EU target) and to reach a share of renewables of 20% by 2020 and at least 27% by 2030. Today, there is a great concern about the conflict between energy and the environment. In this context, it is becoming usual to expect that an extraordinary increase of the use of electricity in the energy production, transport, and consumption will help a sustainable future. Enormous energy savings and exciting enhancements in quality of life will be enabled by new power electronics (PE) energy conversion systems. All energy-consuming devices, from pacemakers and home appliances to electric vehicles and industrial waste processing plants, will be affected. All alternative, sustainable and distributed energy (DE) sources, as well as energy storage systems, will be tied to the smart grid (SG) through swift and efficient PEs converters. For competitive low-carbon renewable energy, transport energy, and smart grid appli- cations, the impact of power electronics is striking where an optimized electrical energy conversion is demanded by the society. Approximately 30% of all electric generated power utilizes power electronics somewhere between the point of generation and its end use. Power electronics is used for more efficient transport, renewable energy production, and distribution including in highly efficient electricity distribution over long distances via high-voltage direct current power lines (HVDC) as well as in the better control of loads in switching power supplies and variable-speed drives for motors that drive fans, pumps, and compressors. By 2030, it is expected that perhaps as much as 80% of all electric power will use power electronics somewhere between generation and consumption. However, with the current state-of-the-art electric equipment, the transformation of the electrical energy occurs with significant losses (in the order of 10% from the source to the point of use) because available semiconductors are not ideal for high power. Materials 2021, 14, 7081. https://doi.org/10.3390/ma14227081 https://www.mdpi.com/journal/materials