Thermally accelerated photochemical damage in CaF2 under DUV irradiation

This paper examined the effects of using 1 nm thickness lubricant thin film combined with additives and deep ultraviolet (UV) irradiation at 185 nm wavelength on the magnetic hard disk to the wear of the magnetic head during contact. Different types and amount of additives were added into the lubricant thin film either with or without deep UV irradiation. A test involved burnishing the magnetic head on the lubricated magnetic hard disk was conducted. The experiment was conducted in a class 100 cleanroom. Contrary to previous studies, the addition of additives into the lubricant film did not lead to a decrease in the amount of wear to the magnetic head. Without deep UV irradiation, the lubricant film combined with additives causes more wear to the magnetic head. The effects of using different percentages of cyclotriphosphazene based additives in perfluoropolyether lubricant were also discussed in this paper. We conclude that deep UV irradiation needed if additives were added when the total lubricant thin film thickness is at 1 nm or below.

In order to control the characteristics of porogen-based porous SiOC film (k ≪ 2.5), we investigated its dependence on the wavelengths of ultraviolet (UV) light by using methods of FT-IR, TDS and nano-indentation. As a result, it was found that specific wavelengths of UV light strongly was effective to porous SiOC film production : porogen desorption, mechanical strength improvement, and reduction of the film damage. Vacuum ultraviolet (VUV) irradiation is necessary for porogen desorption. However, after porogen was removed from SiOC film, the energy of VUV irradiation was too high for porous SiOC film and this caused film damage. The energy of deep ultraviolet (DUV) irradiation was sufficient to improve mechanical strength. We propose that UV curing process should be a multi-step process consisting of VUV and DUV irradiation (Figure 1). The first step removes porogen using VUV irradiation. The second step forms robust porous SiOC film using DUV irradiation. A multi-step curing process was used to control the characteristics of porogen-based porous SiOC film.

Resistance-breaking strains of Tomato mosaic virus (ToMV) are emerging in many countries, including Japan. We examined whether deep ultraviolet (UV) irradiation on tomato plants using light-emitting diodes (LEDs) could suppress the expression of ToMV symptoms. We also investigated the optimum wavelength and radiant exposure for suppressing the disease effectively in tomato plants. Among the three wavelengths tested, UV irradiation at 280-290nm had a relatively high suppressive effect on ToMV and resulted in a low incidence of UV damage. Pre-inoculation exposure to UV was effective in suppressing viral disease, indicating that acquired resistance was induced by UV irradiation. UV-B fluence of 0·7-1·4kJm(-2) day(-1) at wavelengths of 280-290nm suppressed ToMV effectively without significant UV damage. Disease caused in tomato plants by resistance-breaking Tomato mosaic virus (ToMV) could be suppressed by ultraviolet (UV)-B irradiation using light-emitting diodes (LEDs). This paves the way for the future management of plant viral diseases using deep UV LEDs.

We fabricated self-aligned coplanar amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs and defined the source/drain region using deep ultraviolet (DUV) irradiation. For our TFTs, source/drain region were well defined to designed dimensions and contact resistance was low value. The electrical properties of the device show field-effect mobility (μFE) of 13.2 cm2/Vs, subthreshold swing (S/S) of 0.32 V/decade, threshold voltage (Vth) of 3.2 V, and on/off ratio of 8.8 × 108, respectively. In addition, the reduced channel length (ΔL) and width-normalized contact resistance (RSDW) were 1.08 μm and 87.5 Ω cm, respectively. Stability behavior of self-aligned coplanar a-IGZO TFT fabricated by DUV irradiation was investigated under negative bias stress (NBS), negative bias illumination stress (NBIS), positive bias stress (PBS), and positive bias temperature stress (PBTS). After the stress under NBS, NBIS, PBS, and PBTS, the Δ Vth values of −0.3 V, −0.8 V, 1.2 V, and 1.3 V were measured, respectively. Additionally, the electrical characteristics of the n+ doping region by DUV irradiation were not degraded under any of the stress conditions.

The electrical properties of p-channel low temperature polycrystalline silicon (LTPS) thin film transistors (TFTs) under deep ultraviolet (UV) irradiation were studied. Characteristics including threshold voltage (Vth), hole field effect mobility (μeff) subthreshold swing (SS), and leakage current (Ioff) were investigated as a function of UV irradiation doses from 4 to 20 J/cm2. With an increase in UV irradiation dosage, the Vth shift of the TFT showed a turnaround effect, which first shifted to the positive direction and then shifted back to the negative direction after a UV irradiation dose of 16 J/cm2. The continuous degradation of SS and μeff was discovered with the enhancement of UV irradiation dose. To better understand the physical mechanisms underlying these characteristic changes, UV induced traps at poly-Si grain boundaries, traps at the poly-Si and gate oxide insulator (poly-Si/SiO2) interface, and trapped charges in the gate oxide were studied with a function of UV irradiation doses.

Low-temperature deposition of inorganic ferroelectric (FE) thin films is highly demanded for lowering the environmental impact through lesser energy consumption. Doped HfO2-based FE thin films commonly require high crystalline temperature (>450 °C) to exhibit ferroelectricity. Here, we report that the crystallization temperature of the metastable orthorhombic (O) phase in Hf0.5Zr0.5O2 thin films can be lowered to 350 °C via a deep ultraviolet (DUV) irradiation process carried out before rapid thermal annealing (RTA). The DUV irradiation initializes a nucleation process of the crystal growth through photochemical cleavage of organic residues, followed by the densification of metal oxide films, and the subsequent RTA at 350 °C crystallizes the Hf0.5Zr0.5O2 thin film with a higher O-phase fraction. The DUV-irradiated films annealed at 350 °C exhibited FE characteristics, whereas the non-irradiated films annealed above 450 °C become FE. Our study suggests that DUV irradiation can be successfully utilized to lower the crystallization temperature of HZO thin films and can lead to the realization of flexible FE random access memories.

Deep ultraviolet (DUV) light spans within the 250 nm to 350 nm invisible wavelength range. Although it strongly damages various cells, the efficacy of DUV irradiation on pancreatic cancer cells has never been clarified. The purpose of this study was to reveal the antitumor effects of DUV irradiation on pancreatic cancer cells. Human pancreatic cancer cell lines were eradicated with DUV or ultraviolet A (UVA) for 5 s. Several angiogenesis-related proteins were studied in cancer cells after DUV irradiation using a protein antibody array. A subcutaneous xenograft model was established by inoculation of pancreatic cancer cells into mice. Tumors in this model were irradiated with DUV or UVA once or twice for two weeks. Tumor volumes in these groups (DUV×1: one irradiation, DUV×2: two irradiations, and untreated) were analyzed one week after the second irradiation. DUV irradiation significantly changed the cytomorphology of pancreatic cancer cells. In addition, DUV irradiation induced apoptosis on pancreatic cancer cells more strongly than UVA irradiation and no irradiation. Interestingly, lower expression of thrombospondin 1 (TSP1) and tissue inhibitor of metalloproteinase 1 (TIMP1) was identified after DUV treatment. The tumor volume in the DUV-treated groups (DUV×1 and DUV×2) was smaller than that in the untreated group. Further investigations are required to reveal the precise mechanisms of the antitumor effects of DUV irradiation and to facilitate its clinical application as a new therapy for pancreatic cancer. Overall, DUV irradiation can be potentially used as a therapeutic option of pancreatic malignancy.

The surface modification of a double-decker-shaped polysilsesquioxane (DDPSQ) film by deep ultraviolet (UV) irradiation (λ = 185 and 254 nm) was studied in the presence of atmospheric oxygen at room temperature. The change in the surface structure of a DDPSQ hybrid film was observed by means of contact angle measurements, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Exposure to deep UV light was found to convert the surface of DDPSQ film from hydrophobic to hydrophilic due to the formation of silanol groups (Si–OH) on the DDPSQ film. Measurements of FT-IR and XPS indicate that the Si–O–Si cage structure of DDPSQ was converted to the Si–O–Si network structure of SiO2 through cleavage of the Si–O–Si cage with deep UV irradiation. The irradiated DDPSQ film surface is very smooth with a root-mean-square (RMS) roughness of 0.34 nm. Moreover, to demonstrate the effect of surface modification of a DDPSQ film on the adhesion of metals, we fabricated silver (Ag) micropatterns on the deep UV modified DDPSQ film by laser-induced pyrolysis of a film prepared from liquid-dispersed Ag nanoparticles. The Ag micropatterns show an excellent adhesion to the modified DDPSQ surface as assessed by the Scotch tape test.

We report on a compact, high-power, high repetition-rate, ultrafast source of deep ultraviolet (DUV) radiation. Using a Yb-fibre laser at 1064 nm producing 260 fs output pulses at a 78 MHz repetition rate and usingtwo stage single-pass frequency-doubling, we have generated ultrafast DUV radiation at 266 nm. The fibre laser is first frequency-doubled into green at 532 nm using a LBO crystal with output power as high as 2.4 W and with a conversion efficiency of ∼ 50%. Further, the generated green is frequency-doubled in BBO crystal generating DUV radiation with an output power as high as 616 mW corresponding with near-IR to DUV conversion efficiency of ∼ 12.8%.

Self-aligned coplanar top gate indium–gallium–zinc-oxide thin-film transistors (TFTs), with source/drain (S/D) regions that were heavily doped by various deep-ultraviolet (DUV) irradiation energies at dual wavelengths of 185 and 254 nm, were investigated. The electrical performances of TFTs improved as the DUV irradiation energy increased. The proposed TFTs, with DUV irradiation of 20 J/cm2, have a field-effect mobility of 22.0 cm2/ $\text {V}\cdot \text {s}$ , a threshold voltage of 2.2 V, a subthreshold swing value of 0.24 V/decade, and an on/off current ratio of $1.34 \times 10^{6}$ . In addition, the channel length modulation ( $\Delta L$ ) and the width-normalized contact resistance ( $R_{\mathrm {SD}}W$ ) were 1.04 $\mu \text{m}$ and 60.5 $\Omega \cdot \text {cm}$ , respectively. Such short $\Delta L$ and low $R_{\mathrm {\mathbf {SD}}}W$ values indicate that the S/D regions were properly formed by the DUV irradiation. This simple and cost-effective doping technique can be useful for the fabrication of self-aligned TFTs.

A deep ultraviolet (DUV) light-emitting diode (LED) is a device that can irradiate electromagnetic waves from 250 nm to 350 nm. Tousled-like kinase 1 (TLK1) encodes a nuclear serine/threonine kinase, which is thought to influence the effects of DUV irradiation in cancer. The aim of this study was to clarify the interaction of TLK1 with DUV irradiation-induced DNA damage in cancer cells. Pancreatic cancer cell lines were treated with or without DUV. TLK1 expression and phosphorylation in the two groups were examined. Then, these cancer cell lines were treated with thioridazine (THD), DUV or both. Thereafter, cytomorphology and apoptosis were assessed. Several proteins related to DNA damage, were analyzed in cancer cells treated with DUV and THD. Tumors in a subcutaneous xenograft model were treated with THD, DUV, or both for six weeks. DUV irradiation induced the phosphorylation of TLK1 in pancreatic cancer cell lines. Cytomorphology was significantly changed in pancreatic cancer cells treated with DUV and THD. TLK1 inhibition enhanced DUV irradiation-induced apoptosis in cancer cells. Interestingly, CHK1 and pCHK1 expression was suppressed after TLK1 inhibition. In addition, inhibition of MRE11 led to a decrease in the expression of CHK1 and pCHK1, accompanied by a notable increase in apoptosis. In the subcutaneous xenograft models, the tumor volume in the DUV and THD groups was lower than that in the other groups. TLK1 phosphorylation is an important event in DUV irradiation. DUV irradiation combined with TLK1 inhibition has therapeutic potential in pancreatic cancer cells.

For field effect transistors (FETs) based on electrospun oxide nanofibers, the electrical stability can be deteriorated by high-temperature annealing treatment. In this work, the self-passivation of an In2O3 nanofiber FET is achieved by the consequent thermal treatment, water treatment, and deep ultraviolet (DUV) irradiation, and the FET is named as a TWD (thermal treatment-water treatment-DUV irradiation)-device. For comparison, the devices treated by thermal treatment and by thermal + water treatment were also fabricated and abbreviated as a T-device and a TW (thermal treatment-water treatment)-device, respectively. From the transfer characteristics of the T-, TW-, and TWD-devices, the electrical performance is first degraded by water treatment and then recovered after DUV irradiation. The positive bias stress test confirms the stability enhancement after TWD treatment, indicating the achievement of the self-passivated FET based on In2O3 nanofibers. The excellent electrical stability is owing to the structural relaxation and the removal of trap sites such as oxygen vacancy and hydroxide. Integrated with the high-k ZrO2 dielectric, the TWD-In2O3/ZrO2 FET exhibits further improved electrical performance, including a mobility of 3.35 cm2/V s and a high on/off current ratio of 107.

The low-temperature electrical passivation of an amorphous oxide semiconductor (AOS) thin-film transistor (TFT) is achieved by a deep ultraviolet (DUV) light irradiation-water treatment-DUV irradiation (DWD) method. The water treatment of the first DUV-annealed amorphous indium-gallium-zinc-oxide (a-IGZO) thin film is likely to induce the preferred adsorption of water molecules at the oxygen vacancies and leads to subsequent hydroxide formation in the bulk a-IGZO films. Although the water treatment initially degraded the electrical performance of the a-IGZO TFTs, the second DUV irradiation on the water-treated devices may enable a more complete metal-oxygen-metal lattice formation while maintaining low oxygen vacancies in the oxide films. Overall, the stable and dense metal-oxygen-metal (M-O-M) network formation could be easily achieved at low temperatures (below 150 °C). The successful passivation of structural imperfections in the a-IGZO TFTs, such as hydroxyl group (OH-) and oxygen vacancies, mainly results in the enhanced electrical performances of the DWD-processed a-IGZO TFTs (on/off current ratio of 8.65 × 10(9), subthreshold slope of 0.16 V/decade, an average mobility of >6.94 cm(2) V(-1) s(-1), and a bias stability of ΔVTH < 2.5 V), which show more than a 30% improvement over the simple DUV-treated a-IGZO TFTs.

The deep ultraviolet photochemistry of aqueous pyruvate is believed to have been essential to the origin of life, and near ultraviolet excitation of pyruvate in aqueous aerosols is assumed to contribute significantly to the photochemistry of the Earth’s atmosphere. However, the primary photochemistry of aqueous pyruvate is unknown. Here we study the susceptibility of aqueous pyruvate to photodissociation by deep ultraviolet and near ultraviolet irradiation with femtosecond spectroscopy supported by density functional theory calculations. The primary photo-dynamics of the aqueous pyruvate show that upon deep-UV excitation at 200 nm, about one in five excited pyruvate anions have dissociated by decarboxylation 100 ps after the excitation, while the rest of the pyruvate anions return to the ground state. Upon near-UV photoexcitation at a wavelength of 340 nm, the dissociation yield of aqueous pyruvate 200 ps after the excitation is insignificant and no products are observed. The experimental results are explained by our calculations, which show that aqueous pyruvate anions excited at 200 nm have sufficient excess energy for decarboxylation, whereas excitation at 340 nm provides the aqueous pyruvate anions with insufficient energy to overcome the decarboxylation barrier.

Dystrophic muscle is characterized by necrosis/regeneration cycles, inflammation, and fibro-adipogenic development. Conventional histological stainings provide essential topographical data of this remodeling but may be limited to discriminate closely related pathophysiological contexts. They fail to mention microarchitecture changes linked to the nature and spatial distribution of tissue compartment components. We investigated whether label-free tissue autofluorescence revealed by Synchrotron deep ultraviolet (DUV) radiation could serve as an additional tool for monitoring dystrophic muscle remodeling. Using widefield microscopy with specific emission fluorescence filters and microspectroscopy defined by high spectral resolution, we analyzed samples from healthy dogs and two groups of dystrophic dogs: naïve (severely affected) and MuStem cell-transplanted (clinically stabilized) animals. Multivariate statistical analysis and machine learning approaches demonstrated that autofluorescence emitted at 420–480 nm by the Biceps femoris muscle effectively discriminates between healthy, dystrophic, and transplanted dog samples. Microspectroscopy showed that dystrophic dog muscle displays higher and lower autofluorescence due to collagen cross-linking and NADH respectively than that of healthy and transplanted dogs, defining biomarkers to evaluate the impact of cell transplantation. Our findings demonstrate that DUV radiation is a sensitive, label-free method to assess the histopathological status of dystrophic muscle using small amounts of tissue, with potential applications in regenerative medicine.