Strain-engineering the hole mobility in off-stoichiometric copper chromium delafossite


CALL: 2019

DOMAIN: MS - New Functional and Intelligent Materials and Surfaces






KEYWORDS: Transparent electronics, transparent oxide semiconductors, electronic properties, charge carriers mobility, thin films

START: 2020-03-01



Submitted Abstract

The greatest challenge in the field of transparent electronics is the lack of a completely transparent p-n junction, the fundamental “brick” in semiconductor device’s technology. Although transparent conducting oxides (TCOs) – materials with a good transparency and a controllable conductivity – are already used in various fields such as solar cells, panel displays or organic light emitting diodes, the lack of a reliable p-type transparent semiconductor results in applications where only passive functions are mostly used. A full transparent electronics will require a high-mobility p-type TOS which properties matching those of actual commercially available n-type semiconductors (Ex: ITO with a conductivity around 1000 S/cm and an optical transparency around 80%, mobility up 50 cm2/V1s1). To match such properties, it is believed that p-type TCOs relying on band transport shall be targeted and that the use of p-type TCOs based on small-polaron transport shall be avoided. However, a very recent article did challenge such a statement, with a specific attention paid to Cr-based oxides . Among others TCOs, copper based delafossites (CuM3+O2) have also shown lately attractive performances as p-type TCOs (conductivity 280 Scm-1 and a visible transmittance of 50 %, ). The conductivity of such materials is known to be assisted by small polaron hopping. This mechanism has usually been considered detrimental for TCO applications due to the low mobility of small polarons compared to band carriers. The aforementioned studies suggest that TCOs relying on small-polaron transport can actually outperform those relying on band transport due to different change of the optical absorption as the carrier concentration increases in the two cases .LIST succeeded in synthesizing the Cu0.66Cr1.33O2, a particular type of copper chromium delafossite demonstrating the best transparencies and conductivities for p-type oxides. Previous work elucidated aspects related to the source of doping and provided methods to control the carriers’ concentration levels in this material. The STTERMOB project aims to tailor the charge carriers’ mobility by engineering the strain induced in Cu0.66Cr1.33O2 p-type delafossite and to provide further understanding of the electrical conduction properties. For the first time the delafossite will be deposited on high flexible transparent glass. Doping of the material in order to induce local strain is also foreseen. Understanding the influence of the strain on the electrical properties of these materials will open new opportunities towards the optimization of the mobility for future applications in active transparent electronics,as well as the tuning of the valence band minimum energy for hole injection layers in opto-electronic devices or optimized p-n junctions.

This site uses cookies. By continuing to use this site, you agree to the use of cookies for analytics purposes. Find out more in our Privacy Statement