Oxidation behavior of AlN/CrN multilayered hard coatings

Abstract We report on the oxidation behavior of AlN/CrN multilayers at 900 °C, deposited by radio frequency magnetron sputtering. It is shown that oxidation in this system is controlled by diffusion of Cr towards the surface and formation of Cr2O3. Cr diffusion is found to mainly occur along grain boundaries. Thus, coherent cubic AlN/CrN multilayer regions with coarse columnar grain structures are found to be oxidation resistant, whereas regions decomposed into hexagonal AlN/cubic CrN are prone to oxidation

Structural and optical properties of (112̅2) InGaN quantum wells compared to (0001) and (112̅0)

We benchmarked growth, microstructure and photo luminescence (PL) of (112-2) InGaN quantum wells (QWs) against (0001) and (112-0). In incorporation, growth rate and the critical thickness of (112-2) QWs are slightly lower than (0001) QWs, while the In incorporation on (112-0) is reduced by a factor of three. A small step-bunching causes slight fluctuations of the emission wavelength. Transmission electron microscopy as well as atom probe tomography (APT) found very flat interfaces with little In segregation even for 20% In content. APT frequency distribution analysis revealed some deviation from a random InGaN alloy, but not as severe as for (112-0). The slight deviation of (112-2) QWs from an ideal random alloy did not broaden the 300 K PL, the line widths were similar for (112-2) and (0001) while (112-0) QWs were broader. Despite the high structural quality and narrow PL, the integrated PL signal at 300 K was about 4 lower on (112-2) and more than 10 lower on (112-0)

Structural and optical properties of (112̅2) InGaN quantum wells compared to (0001) and (112̅0)

We benchmarked growth, microstructure and photo luminescence (PL) of (11$\bar 2$2) InGaN quantum wells (QWs) against (0001) and (11$\bar 2$0). In incorporation, growth rate and the critical thickness of (11$\bar 2$2) QWs are slightly lower than (0001) QWs, while the In incorporation on (11$\bar 2$0) is reduced by a factor of three. A small step-bunching causes slight fluctuations of the emission wavelength. Transmission electron microscopy as well as atom probe tomography (APT) found very flat interfaces with little In segregation even for 20% In content. APT frequency distribution analysis revealed some deviation from a random InGaN alloy, but not as severe as for (11$\bar 2$0). The slight deviation of (11$\bar 2$2) QWs from an ideal random alloy did not broaden the 300 K PL, the line widths were similar for (11$\bar 2$2) and (0001) while (11$\bar 2$0) QWs were broader. Despite the high structural quality and narrow PL, the integrated PL signal at 300 K was about 4$\times$ lower on (11$\bar 2$2) and more than 10$\times$ lower on (11$\bar 2$0).This work was supported by EU-FP7 ALIGHT No. NMP- 2011-280587 and the UK Engineering and Physical Sciences Research Council No. EP/I012591/1.This is the final version of the article. It first appeared from IOP Publishing via http://dx.doi.org/10.1088/0268-1242/31/8/08500