New approaches for achieving more perfect transition metal oxide thin films

Abstract

This perspective considers the enormous promise of epitaxial functional transition metal oxide thin films for future applications in low power electronic and energy applications since they offer wide-ranging and highly tunable functionalities and multifunctionalities, unrivaled among other classes of materials. It also considers the great challenges that must be overcome for transition metal oxide thin films to meet what is needed in the application domain. These challenges arise from the presence of intrinsic defects and strain effects, which lead to extrinsic defects. Current conventional thin film deposition routes often cannot deliver the required perfection and performance. Since there is a strong link between the physical properties, defects and strain, routes to achieving more perfect materials need to be studied. Several emerging methods and modifications of current methods are presented and discussed. The reasons these methods better address the perfection challenge are considered and evaluated.

Defects in complex oxide thin films for electronics and energy applications: challenges and opportunities

“…Recently, with the simultaneous advances in thin film synthesis, characterization, and modelling of TMOs, engineering the defects and interface in TMOs have been widely explored as a route to enhance and even create novel functionalities in TMOs for new devices. 1 Although significant progresses have been made in the past decade (will be discussed later), a deep understanding of the defect chemistry in complex TMOs still lag behind that in conventional semiconductors. This is because: (1) TMOs have many constituent elements and can accommodate a wide variety of defects, including oxygen vacancies (V O ), cation vacancies (V C ), interstitial defects, local structural distortions, grain boundaries, domain walls, misfit dislocations, and impurities such as H +/À , Li + , etc.…”

“…1 Although significant progresses have been made in the past decade (will be discussed later), a deep understanding of the defect chemistry in complex TMOs still lag behind that in conventional semiconductors. This is because: (1) TMOs have many constituent elements and can accommodate a wide variety of defects, including oxygen vacancies (V O ), cation vacancies (V C ), interstitial defects, local structural distortions, grain boundaries, domain walls, misfit dislocations, and impurities such as H +/À , Li + , etc. (2) Due to the ionic nature of TMOs, the transition energy of defects in TMOs are usually high and the extra charges left by defects are usually localized, therefore defects in TMOs usually cannot lead to a significant change in the electrical conductivity as present in conventional semiconductors.…”

Overcoming Phase‐Purity Challenges in Complex Metal Oxide Photoelectrodes: A Case Study of CuBi2O4

“…[25,26] Physical synthesis approaches (i.e., pulsed laser deposition, molecular beam epitaxy) of high-quality metal-oxides thin films have been developed and continuously improved in the past three decades. [27] Common denominators in these methods are the use of lattice-matched substrates materials, which enable epitaxial growth, and the ability to deposit and/or post-anneal at high temperatures (≤1000 °C). However, the majority of thinfilm photoelectrodes are polycrystalline and involve the use of polycrystalline transparent conductive substrates with moderated thermal stabilities (≤550 °C) in their fabrication.…”

Nickel oxide thin films grown by chemical deposition techniques: Potential and challenges in next‐generation rigid and flexible device applications

“…Other mechanisms involve tuning the Schottky barrier height, as well as charge‐trapping processes which are highly dependent on defect concentration. All switching processes relate to control of defect concentration, but this is difficult to achieve in oxides by standard deposition methods 182 . To achieve greater performance in oxides, elimination of conductive filaments is necessary, as well as very careful control of oxygen vacancy concentrations, other intrinsic defect concentrations, and background electronic concentrations.…”