Enhancement of electrical characteristics and stability of self-patterned In–Zn–O thin-film transistors based on photosensitive precursors

We report a novel self-patterning method for solution-processed indium zinc oxide (IZO) thin films based on photosensitive precursors. This approach is an alternative and evolutionary approach to the traditional photoresist patterning techniques. Chelate bonds between metal ions and β-diketone compounds in ultraviolet light-exposed IZO solutions provided intrinsic photosensitivity, which resulted in a solubility difference between exposed and non-exposed regions. This difference enabled self-patterning of the IZO for thin-film transistor (TFT) fabrication. Compared with previously reported self-patterning methods based on photosensitive activators, our self-patterned IZO TFTs based on photosensitive precursors displayed excellent electrical characteristics and stability. The field-effect mobility increased from 0.27 to 0.99 cm2/Vs, the subthreshold swing decreased from 0.54 to 0.46 V/dec, and the threshold voltage shift under a positive bias stress test (1,000 s) improved from 9.32 to 1.68 V. The photosensitive precursor played a key role in these improvements permitting fewer organic species which act as defect sites after metal oxide formation. Consequently, our approach compares favorably with that of conventional fabrication process using photoresist in terms of its simplicity, cost efficiency, and electrical performance.

Резистивное переключение в структурах металл-оксид-полупроводник с наноостровками GeSi на подложке кремния

The self-assembled GeSi nanoislands built into the semiconductor-insulator interface of the MOS-structures based on Si(001) with SiOx and ZrO2(Y) oxide layers deposited by magnetron sputtering have been shown to initiate bipolar resistive switching without preliminary electroforming. The current-voltage curves and electrical parameters of the MOS-structures in the high-resistance state and in the low-resistance state have been studied. A change in the built-in charge in the dielectric near the insulator-semiconductor interface during resistive switching is established and associated with the formation and destruction of conductive filaments. The light-stimulated resistive switching of MOS-structures with ZrO2(Y) layer from the high-resistance to the low-resistance state is observed, which is associated with an increase in the conductivity of the space-charge region in the Si substrate due to interband optical absorption in Si, which causes a voltage redistribution between Si and ZrO2(Y) layer. A difference in the shape of the small signal photo-voltage spectra of MOS-structures is found in the spectral region of intrinsic photosensitivity of Si in the high and low resistance states due to the leakage of photo-excited charge carriers from Si to the metal electrode through filaments.

Влияние импульсного гамма-нейтронного облучения на фоточувствительность фотодиодов на базе Si с наноостровками GeSi и эпитаксиальными слоями Ge

A comparative study of the effect of pulsed γ-neutron irradiation on the photosensitivity spectra of Si p – n photodiodes with active layers based on self-assembled GeSi nanoisland arrays and Ge epitaxial layers is performed. The irradiation of photodiodes with GeSi nanoislands is found to not lead to photosensitivity degradation in the spectral region of interband optical absorption in nanoislands (wavelength range of 1.1–1.7 μm). At the same time, a steady decrease in the intrinsic photosensitivity of Si and the photosensitivity of photodiodes based on Ge epitaxial layers with an increase in irradiation dose is observed. This effect is attributed to the accumulation of radiation-induced defects in the Si matrix and deep in Ge epitaxial layers, respectively.

Horizontal cells expressing melanopsin x are novel photoreceptors in the avian inner retina

In the vertebrate retina, three types of photoreceptors—visual photoreceptor cones and rods and the intrinsically photosensitive retinal ganglion cells (ipRGCs)—converged through evolution to detect light and regulate image- and nonimage-forming activities such as photic entrainment of circadian rhythms, pupillary light reflexes, etc. ipRGCs express the nonvisual photopigment melanopsin (OPN4), encoded by two genes: the Xenopus (Opn4x) and mammalian (Opn4m) orthologs. In the chicken retina, both OPN4 proteins are found in ipRGCs, and Opn4x is also present in retinal horizontal cells (HCs), which connect with visual photoreceptors. Here we investigate the intrinsic photosensitivity and functioning of HCs from primary cultures of embryonic retinas at day 15 by using calcium fluorescent fluo4 imaging, pharmacological inhibitory treatments, and Opn4x knockdown. Results show that HCs are avian photoreceptors with a retinal-based OPN4X photopigment conferring intrinsic photosensitivity. Light responses in HCs appear to be driven through an ancient type of phototransduction cascade similar to that in rhabdomeric photoreceptors involving a G-protein q, the activation of phospholipase C, calcium mobilization, and the release of the inhibitory neurotransmitter GABA. Based on their intrinsic photosensitivity, HCs may have a key dual function in the retina of vertebrates, potentially regulating nonvisual tasks together with their sister cells, ipRGCs, and with visual photoreceptors, modulating lateral interactions and retinal processing.