Electrical and dielectric parameters in TiO2-NW/Ge-NW heterostructure MOS device synthesized by glancing angle deposition technique

AbstractThis paper reports the catalyst-free coaxial TiO2/Ge-nanowire (NW) heterostructure synthesis using the glancing angle deposition (GLAD) technique integrated into an electron beam evaporator. The frequency and voltage dependence of the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) characteristics of an Ag/TiO2-NW/Ge-NW/Si device over a wide range of frequency (10 kHz–5 MHz) and voltage (− 5 V to + 5 V) at room temperature were investigated. The study established strong dependence on the applied frequency and voltage bias. Both C–V and G/ω–V values showed wide dispersion in depletion region due to interface defect states (Dit) and series resistance (Rs). The C and G/ω value decreases with an increase in applied frequency. The voltage and frequency-dependent Dit and Rs were calculated from the Hill-Coleman and Nicollian–Brews methods, respectively. It is observed that the overall Dit and Rs for the device decrease with an increase in the frequency at different voltages. The dielectric properties such as dielectric constant ($$\upepsilon$$ ϵ ′), loss ($$\upepsilon$$ ϵ ″) and loss tangent (tan δ) were determined from the C–V and G/ω–V measurements. It is observed that $$\upepsilon$$ ϵ ′, $$\upepsilon$$ ϵ ″ decreases with the increase in frequency. Therefore, the proposed MOS structure provides a promising alternative approach to enhance the device capability in the opto-electronics industry.

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Glancing Angle Deposition and Growth Mechanism of Inclined AlN Nanostructures Using Reactive Magnetron Sputtering

Coatings ◽

10.3390/coatings10080768 ◽

2020 ◽

Vol 10 (8) ◽

pp. 768

Author(s):

Samiran Bairagi ◽

Kenneth Järrendahl ◽

Fredrik Eriksson ◽

Lars Hultman ◽

Jens Birch ◽

...

Keyword(s):

Magnetron Sputtering ◽

Growth Mechanism ◽

Strong Dependence ◽

Glancing Angle Deposition ◽

Reactive Magnetron Sputtering ◽

Average Particle ◽

Reactive Magnetron ◽

Working Pressure ◽

Glancing Angle ◽

Angle Deposition

Glancing angle deposition (GLAD) of AlN nanostructures was performed at room temperature by reactive magnetron sputtering in a mixed gas atmosphere of Ar and N2. The growth behavior of nanostructures shows strong dependence on the total working pressure and angle of incoming flux. In GLAD configuration, the morphology changed from coalesced, vertical nanocolumns with faceted terminations to highly inclined, fan-like, layered nanostructures (up to 38°); while column lengths decreased from around 1743 to 1068 nm with decreasing pressure from 10 to 1.5 mTorr, respectively. This indicates a change in the dominant growth mechanism from ambient flux dependent deposition to directional ballistic shadowing deposition with decreasing working pressures, which is associated with the change of energy and incident angle of incoming reactive species. These results were corroborated using simulation of metal transport (SiMTra) simulations performed at similar working pressures using Ar and N separately, which showed the average particle energy and average angle of incidence decreased while the total average scattering angle of the metal flux arriving at substrate increased with increasing working pressures. Observing the crystalline orientation of GLAD deposited wurtzite AlN nanocolumns using X-ray diffraction (XRD), pole-figure measurements revealed c-axis <0001> growth towards the direction of incoming flux and a transition from fiber-like to biaxial texture took place with increasing working pressures. Under normal deposition conditions, AlN layer morphology changed from {0001} to {101¯1} with increasing working pressure because of kinetic energy-driven growth.

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