TY - JOUR
T1 - Origin of high carrier mobility and low residual stress in RF superimposed DC sputtered Al doped ZnO thin film for next generation flexible devices
AU - Kumar, Naveen
AU - Dubey, Ashish
AU - Bahrami, Behzad
AU - Venkatesan, S.
AU - Qiao, Qiquan
AU - Kumar, Mukesh
N1 - Funding Information:
We sincerely acknowledge IIT Ropar for SEED grant and funding through interdisciplinary Solar PV project. One of the author (NK) sincerely acknowledge IIT Ropar for senior research fellowship. Author also acknowledges CeNSE, IISc Bangalore for availing the XRD and XPS facility.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2018/4/1
Y1 - 2018/4/1
N2 - In this work, the energy and flux of high energetic ions were controlled by RF superimposed DC sputtering process to increase the grain size and suppress grain boundary potential with minimum residual stress in Al doped ZnO (AZO) thin film. AZO thin films were deposited at different RF/(RF + DC) ratios by keeping total power same and were investigated for their electrical, optical, structural and nanoscale grain boundaries potential. All AZO thin film showed high crystallinity and orientation along (002) with peak shift as RF/(RF + DC) ratio increased from 0.0, pure DC, to 1.0, pure RF. This peak shift was correlated with high residual stress in as-grown thin film. AZO thin film grown at mixed RF/(RF + DC) of 0.75 showed high electron mobility, low residual stress and large crystallite size in comparison to other AZO thin films. The nanoscale grain boundary potential was mapped using Kelvin Probe Force Microscopy in all AZO thin film and it was observed that carrier mobility is controlled not only by grains size but also by grain boundary potential. The XPS analysis confirms the variation in oxygen vacancies and zinc interstitials which explain the origin of low grain boundaries potential and high carrier mobility in AZO thin film deposited at 0.75 RF/(RF + DC) ratio. This study proposes a new way to control the grain size and grain boundary potential to further tune the optoelectronic-mechanical properties of AZO thin films for next generation flexible and optoelectronic devices.
AB - In this work, the energy and flux of high energetic ions were controlled by RF superimposed DC sputtering process to increase the grain size and suppress grain boundary potential with minimum residual stress in Al doped ZnO (AZO) thin film. AZO thin films were deposited at different RF/(RF + DC) ratios by keeping total power same and were investigated for their electrical, optical, structural and nanoscale grain boundaries potential. All AZO thin film showed high crystallinity and orientation along (002) with peak shift as RF/(RF + DC) ratio increased from 0.0, pure DC, to 1.0, pure RF. This peak shift was correlated with high residual stress in as-grown thin film. AZO thin film grown at mixed RF/(RF + DC) of 0.75 showed high electron mobility, low residual stress and large crystallite size in comparison to other AZO thin films. The nanoscale grain boundary potential was mapped using Kelvin Probe Force Microscopy in all AZO thin film and it was observed that carrier mobility is controlled not only by grains size but also by grain boundary potential. The XPS analysis confirms the variation in oxygen vacancies and zinc interstitials which explain the origin of low grain boundaries potential and high carrier mobility in AZO thin film deposited at 0.75 RF/(RF + DC) ratio. This study proposes a new way to control the grain size and grain boundary potential to further tune the optoelectronic-mechanical properties of AZO thin films for next generation flexible and optoelectronic devices.
KW - Aluminium doped zinc oxide (AZO)
KW - Grain boundary potential
KW - Hall mobility
KW - Kelvin probe force microscopy (KPFM)
KW - RF/(RF+DC) ratio
KW - Residual stress
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U2 - 10.1016/j.apsusc.2017.11.274
DO - 10.1016/j.apsusc.2017.11.274
M3 - Article
AN - SCOPUS:85042212896
SN - 0169-4332
VL - 436
SP - 477
EP - 485
JO - Applied Surface Science
JF - Applied Surface Science
ER -