Angle-dependent X-ray photoelectron spectroscopy study of the evolution of GaAs(Cs,O) surface during "high-low temperature" activation

Low-temperature activation of oxide semiconductor materials such as In-Ga-Zn-O (IGZO) is a key approach for their utilization in flexible devices. We previously reported that the activation temperature can be reduced to 150 °C by hydrogen-doped IGZO (IGZO:H), demonstrating a strong potential of this approach. In this paper, we investigated the mechanism for reducing the activation temperature of the IGZO:H films. In situ Hall measurements revealed that oxygen diffusion from annealing ambient into the conventional Ar/O2-sputtered IGZO film was observed at >240 °C. Moreover, the temperature at which the oxygen diffusion starts into the film significantly decreased to 100 °C for the IGZO:H film deposited at hydrogen gas flow ratio (R[H2]) of 8%. Hard X-ray photoelectron spectroscopy indicated that the near Fermi level (EF) defects in the IGZO:H film after the 150 °C annealing decreased in comparison to that in the conventional IGZO film after 300 °C annealing. The oxygen diffusion into the film during annealing plays an important role for reducing oxygen vacancies and subgap states especially for near EF. X-ray reflectometry analysis revealed that the film density of the IGZO:H decreased with an increase in R[H2] which would be the possible cause for facilitating the O diffusion at low temperature.

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X-ray photoelectron spectroscopy study of low-temperature molybdenum oxidation process

Journal of Applied Physics ◽

10.1063/1.370690 ◽

1999 ◽

Vol 85 (12) ◽

pp. 8415-8418 ◽

Cited By ~ 24

Author(s):

S. I. Castañeda ◽

I. Montero ◽

J. M. Ripalda ◽

N. Dı́az ◽

L. Galán ◽

...

Keyword(s):

Low Temperature ◽

Photoelectron Spectroscopy ◽

Oxidation Process ◽

Spectroscopy Study ◽

X Ray

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CO2 Methanation: Nickel–Alumina Catalyst Prepared by Solid-State Combustion

Materials ◽

10.3390/ma14226789 ◽

2021 ◽

Vol 14 (22) ◽

pp. 6789

Author(s):

Olga Netskina ◽

Svetlana Mucha ◽

Janna Veselovskaya ◽

Vasily Bolotov ◽

Oxana Komova ◽

...

Keyword(s):

Solid State ◽

Low Temperature ◽

Photoelectron Spectroscopy ◽

Combustion Method ◽

Nickel Aluminum ◽

Alumina Catalyst ◽

Co2 Methanation ◽

X Ray ◽

Temperature Programmed ◽

Temperature Activation

The development of solvent-free methods for the synthesis of catalysts is one of the main tasks of green chemistry. A nickel–alumina catalyst for CO2 methanation was synthesized by solid-state combustion method using hexakis-(imidazole) nickel (II) nitrate complex. Using X-ray Powder Diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Hydrogen temperature-programmed reduction (H2-TPR), it was shown that the synthesized catalyst is characterized by the localization of easily reduced nickel oxide on alumina surface. This provided low-temperature activation of the catalyst in the reaction mixture containing 4 vol% CO2. In addition, the synthesized catalyst had higher activity in low-temperature CO2 methanation compared to industrial NIAP-07-01 catalyst, which contained almost three times more hard-to-reduce nickel–aluminum spinel. Thus, the proposed approaches to the synthesis and activation of the catalyst make it possible to simplify the catalyst preparation procedure and to abandon the use of solvents, which must be disposed of later on.

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