ALD of Transparent Semiconducting Oxide CuCrO2 for Invisible electronics

So you learn something new every day and as before and so many times also this time from Aalto University, Helsinki Finland! ALD of Transparent Semiconducting Oxide CuCrO2 for Invisible electronics! Some basic facts from this excellent ALD paper :

• Copper chromium oxide CuCrO2 is a member of the delafossite family CuAO2 (A = Al, Cr, Fe, Co, Ga, Y, In, La, Nd, and Eu.
• With predominantly antiferromagnetic interactions, members of this family possess a geometrically frustrated (!) triangular lattice
• The discovery of simultaneous p-type electrical conductivity and optical transparency in CuAlO2 thin films opened the new venue of research among delafossites for ‘invisible electronics’
• CuCrO2  is reported to have the highest electrical conductivity (220 S/cm) among the delafossite materials.
• The need for p-type TCOs stems from the realization of transparent electronics; that by far depends on the p-type semiconductor materials for use in transparent p–n and p–i–n diodes.
• Materials with a wide bandgap (>3 eV), high electrical conductivity, high mobility, low fabrication cost along with controllable transparency would be a boom for transparent electronics. 

ALD  CuCrO2 : check, check, check, check, check

So there is an industrial need for high performing TCO material (we knew that, see Mr Lytle below) with low production cost (always the case) with additional material properties and a upcoming disruptive technology - Invisible Electronics. Doesn´t look like CVD and PVD can make all this  - As always ALD must be up for the challenge!

William O. Lytle the inventor of Electric glass so called Nesa coated glass (Science 1946, Sep. 16) showing of his product which in a way is one of teh first invisible electronic devices. Note that he is using rather thick rubber gloves  to not disturb the device... [http://publica.fraunhofer.de/documents/N-313429.html]

Atomic Layer Deposition of Transparent Semiconducting Oxide CuCrO2 Thin Films

Tripurari S. Tripathi, Janne-Petteri Niemelä and Maarit Karppinen
J. Mater. Chem. C, 2015, Accepted Manuscript
DOI: 10.1039/C5TC01384D

Atomic layer deposition (ALD) is a vital gas-phase technique for atomic-level thickness-controlled deposition of high-quality thin films on various substrate morphologies owing to its self-limiting gas-surface reaction mechanism. Here we report the ALD fabrication of thin films of the semiconducting CuCrO2 oxide that is a highly prospective candidate for transparent electronics applications. In our process, copper 2,2,6,6-tetramethyl-3,5-heptanedionate (Cu(thd)2) and chromium acetyl acetonate (Cr(acac)3) are used as the metal precursors and ozone as the oxygen source. Smooth and homogeneous thin films with an accurately controlled metal composition can be deposited in the temperature range of 240–270 oC; a post-deposition anneal at 700-950oC in an Ar atmosphere then results in well crystalline films with the delafossite structure. The direct bandgap is determined from UV-vis spectrophotometric measurements to be 3.09 eV. The observed transmittance is greater than 75% in the visible range.