Residual stress induced crystalline to amorphous phase transformation in Nb{sub 2}O{sub 5} quantum dots

Journal Article · Mon Jul 28 00:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4890339· OSTI ID:22308513

Dhawan, Sahil; Vedeshwar, Agnikumar G. ^[1]; Dhawan, Tanuj ^[2]

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1. Thin Film Laboratory, Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)
2. Department of Physics and Electronics, Hans Raj College, University of Delhi, Delhi 110007 (India)

Nb{sub 2}O{sub 5} quantum dots (QDs) were grown using a simple technique of vacuum thermal evaporation. QDs were found to be crystalline in nature by selected area electron diffraction (SAED) in TEM. Samples with thickness up to 20 nm did not show any significant residual strain. Residual stress effect on band gap of crystalline Nb{sub 2}O{sub 5} was studied for films thicker than 20 nm. Residual strain was determined using SAED of the films with reference to powder X-ray diffraction (XRD). Films thicker than 45 nm become amorphous as analyzed by both SAED and XRD. The optical absorption of films in the range 25–60 nm indicates significantly varying optical band gap of films. The varying band gap with film thickness scales linearly very well with the variation of residual stress with film thickness. The residual stress dependence of band gap of crystalline films yields stress free band gap as 3.37 eV with pressure coefficient of band gap (∂E{sub g}/∂P){sub T} = −29.3 meV/GPa. From this study, the crystalline to amorphous transformation in tetragonal form of M-Nb{sub 2}O{sub 5} has been determined to be at about 14 GPa. Both pressure coefficient of band gap and crystalline to amorphous transition for tetragonal M-Nb{sub 2}O{sub 5} have been determined for the first time in the literature.

• OSTI ID: 22308513
• Journal Information: Journal of Applied Physics, Vol. 116, Issue 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
AMORPHOUS STATE
ELECTRON DIFFRACTION
EVAPORATION
FILMS
NIOBIUM OXIDES
PHASE TRANSFORMATIONS
POWDERS
PRESSURE COEFFICIENT
PRESSURE RANGE GIGA PA
QUANTUM DOTS
RESIDUAL STRESSES
STRAINS
TETRAGONAL LATTICES
THICKNESS
TRANSFORMATIONS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION