arXiv subjects

Jose Kurian

Publications and source records attributed to Jose Kurian.

3 recordsLinked to original sources

arXiv2012

Physical properties and band structure of reactive molecular beam epitaxy grown oxygen engineered HfO$_{2\pm x}$

We have conducted a detailed thin film growth structure of oxygen engineered monoclinic HfO$_{2\pm x}$ grown by reactive molecular beam epitaxy (MBE). The oxidation conditions induce a switching between ($\bar{1}11$) and (002) texture of hafnium oxide. The band gap of oxygen deficient hafnia decreases with increasing amount of oxygen vacancies by more than 1 eV. For high oxygen vacancy concentrations, defect bands form inside the band gap that induce optical transitions and $p$-type conductivity. The resistivity changes by several orders of magnitude as a function of oxidation conditions. Oxygen vacancies do not give rise to ferromagnetic behavior.

cond-mat.mtrl-sci↗

arXiv2011

Controlled oxygen vacancy induced p-type conductivity in HfO{2-x} thin films

We have synthesized highly oxygen deficient HfO$_{2-x}$ thin films by controlled oxygen engineering using reactive molecular beam epitaxy. Above a threshold value of oxygen vacancies, p-type conductivity sets in with up to 6 times 10^{21} charge carriers per cm3. At the same time, the band-gap is reduced continuously by more than 1 eV. We suggest an oxygen vacancy induced p-type defect band as origin of the observed behavior.

cond-mat.mtrl-sci↗

arXiv2004

Low Microwave Surface Resistance in NdBa2Cu3O7-d Films Grown by Molecular Beam Epitaxy

We report the growth of NdBa2Cu3O7-d films on (100) MgO substrate by Molecular Beam Epitaxy (MBE). Large area NdBa2Cu3O7-d films with homogeneous superconducting properties were grown by precise control of stoichiometry and the optimisation of growth parameters. The stoichiometric ratio of Nd:Ba:Cu close to 1:2:3 yields films with TC of 94 K and JC values above 3.5 MA/cm2 at 77 K on bare MgO substrate. The NdBa2Cu3O7-d films grown under optimised conditions had excellent in-plane texture and good metallicity. The most significant characteristic of our MBE grown NdBa2Cu3O7-d films is the very low microwave surface resistance values at all temperature range compared to its YBa2Cu3O7-d counterpart with typical value of ~870 micro-ohm at 77 K & 22 GHz. Our results on the MBE grown NdBa2Cu3O7-d films suggests that NdBa2Cu3O7-d is a superior choice for the realisation of commercial microwave applications.

cond-mat.supr-con↗