Electrostatic modification of novel materials

Abstract

Application of the field-effect transistor principle to novel materials to achieve electrostatic doping is a relatively new research area. It may provide the opportunity to bring about modifications of the electronic and magnetic properties of materials through controlled and reversible changes of the carrier concentration without modifying the level of disorder, as occurs when chemical composition is altered. As well as providing a basis for new devices, electrostatic doping can in principle serve as a tool for studying quantum critical behavior, by permitting the ground state of a system to be tuned in a controlled fashion. In this paper progress in electrostatic doping of a number of materials systems is reviewed. These include structures containing complex oxides, such as cuprate superconductors and colossal magnetoresistive compounds, organic semiconductors, in the form of both single crystals and REVIEWS OF MODERN PHYSICS, VOLUME 78, OCTOBER-DECEMBER 20060034-6861/2006/78͑4͒/1185͑28͒ ©2006 The American Physical Society 1185 thin films, inorganic layered compounds, single molecules, and magnetic semiconductors. Recent progress in the field is discussed, including enabling experiments and technologies, open scientific issues and challenges, and future research opportunities. For many of the materials considered, some of the results can be anticipated by combining knowledge of macroscopic or bulk properties and the understanding of the field-effect configuration developed during the course of the evolution of conventional microelectronics. However, because electrostatic doping is an interfacial phenomenon, which is largely an unexplored field, real progress will depend on the development of a better understanding of lattice distortion and charge transfer at interfaces in these systems.

Charge Transfer in Iridate-Manganite Superlattices

“…There have been a large number of reports along this direction [10], and we anticipate this field will continue to grow rapidly [11]. Because of the renewed interest in the relativistic spinorbit coupling (SOC) with correlations, iridium-based systems have started to attract significant interest [12].…”

Hopping transport and the Hall effect near the insulator–metal transition in electrochemically gated poly(3-hexylthiophene) transistors

“…In one of the most important recent advances in organic electronics, this value has now been surpassed in electrostatically gated surface layers of single-crystal small molecule semiconductors such as rubrene (for example, refs 14 and 15). Electrostatic gating in the field-effect transistor geometry is ideal for such studies, as it enables wide-range tuning of the carrier density in a single sample 16 . A clear crossover to band transport has indeed been detected in such devices, via observation of a phonon-limited temperature dependence of the mobility, a robust Hall effect, and equivalence of the Hall mobility and the mobility extracted from gate voltagedependent measurements 14,15 .…”

Ferroelectric Field Effect Control of Magnetism in Multiferroic Heterostructures

“…The amount of charge carrier modulation required will depend on the particular system. For strongly correlated oxides, where typical carrier densities are of the order of 10 21 cm −3 , the requisite modulation in the charge carrier doping can be achieved by using a ferroelectric for the gate dielectric, an approach termed the ferroelectric field effect Ahn et al (2006); Venkatesan et al (2007). In this approach to electrostatic doping, the charge carriers screen the large surface bound charge of the ferroelectric; for a ferroelectric such as Pb(Zr,Ti)O 3 (PZT), the charge carrier modulation is of the order of 10 14 cm −2 , much larger than is possible to attain using silicon oxide as the gate dielectric Ahn et al (2003).…”