β-Ga 2 O 3 is one of the most promising wide-bandgap materials for optoelectronic applications as well as a conducting substrate for GaN-based device technologies. Single crystals of undoped β-Ga 2 O 3 are grown by the optical floating zone technique utilizing compressed dry air as growth atmosphere. The properties of β-Ga 2 O 3 are highly anisotropic. Optimization of the processing recipe for wafers along different orientations suitable for device development is conducted. Structural, optical, and electrical properties of the wafers are determined. Efforts are made to fabricate Schottky diodes based on Pt/Ti/Au-β-Ga 2 O 3 -Ti/Au device structures. Devices are fabricated on (À201) cut wafers. The device characteristics are discussed in detail.
Undoped and Sn-doped β-Ga2O3 single crystals were grown by optical floating zone technique by varying the doping concentration of Sn from 0.05 wt % to 0.2 wt %. Uniform distribution of the dopant ions was achieved by heat treatment. The crystalline quality and the expansion of the lattice were observed from the PXRD. Raman spectra reveals the incorporation of Sn atoms into the lattice by replacing Ga in the octahedral site. The interplanar distance (d) was calculated as 2.39 Å from the HR-TEM micrographs. The transmittance was found to be decreasing from 80% to 78% as the concentration of Sn increases. The absorption spectra shows a cut off edge around 260 nm for undoped and 270 nm for all Sn doped samples. The bandgap obtained for undoped β-Ga2O3 was 4.36 eV. The doping of 0.05 wt% of Sn decrease the value of bandgap to 4.08 eV, but, for 0.1 wt% and 0.2 wt% Sn an increase in the bandgap value of 4.13 eV and 4.20 eV was observed respectively. The refractive index was found to be 1.96 at 500 nm wavelength. The increase in Sn concentration results in increase of the roughness from 1.116 nm to 3.511 nm.
Paper-based lightweight, degradable, low-cost, and eco-friendly
substrates are extensively used in wearable biosensor applications,
albeit to a lesser extent in sensing acetone and other gas-phase analytes.
Generally, rigid substrates with heaters have been employed to develop
acetone sensors due to the high operating/recovery temperature (typically
above 200 °C), limiting the use of papers as substrates in such
sensing applications. In this work, we proposed fabricating the paper-based,
room-temperature-operatable acetone sensor using ZnO-polyaniline-based
acetone-sensing inks by a facile fabrication method. The fabricated
paper-based electrodes showed good electrical conductivity (80 S/m)
and mechanical stability (∼1000 bending cycles). The acetone
sensors showed a sensitivity of 0.02/100 ppm and 0.6/10 μL with
an ultrafast response (4 s) and recovery time (15 s) at room temperature.
The sensors delivered a broad sensitivity over a physiological range
of 260 to >1000 ppm with R
2 > 0.98
under
atmospheric conditions. Further, the role of the surface, interfacial,
microstructure, electrical, and electromechanical properties of the
paper-based sensor devices has been correlated with the sensitivity
and room-temperature recovery observed in our system. These versatile,
green, flexible electronic devices would be ideal for low-cost, highly
regenerative, room-/low-temperature-operable wearable sensor applications.
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