Graphene is known to have various specific properties, so that many types of graphene devices are proposed and fabricated. Novolac resist is commonly used to fabricate graphene sensors. Because graphene is composed of six-membered rings of carbon atoms, graphene is thought to be contaminated with the novolac resist by π-π stacking between graphene and the benzene rings of the novolac resin contained in the novolac resist. The transfer characteristics of graphene field effect transistors (FETs) were used to evaluate the graphene deterioration by fabrication resist. Decreasing the number of novolac resist processes on graphene was effective in suppressing the deterioration of graphene. To avoid the π-π stacking between graphene and the aromatic rings, the novolac resist was changed to the acryl resist, the base resin of which does not contain aromatic rings. The PAG that has a steric hindrance from approaching a graphene sheet was effective in suppressing the deterioration compared with the PAG without the steric hindrance. These measures suppressed the deterioration of graphene and improved the transfer characteristics of graphene FETs.

In this study, we have investigated a UV-induced chemical foaming method to create a nanocellular polymer thin film. A small amount of photoacid generator (PAG) was mixed with poly(methyl methacrylate-co-tert-butyl acrylate) (PMMA-co-PtBA). After UV irradiation followed by heating, tert-butyl ester group in the PtBA was deprotected with the acid generated from the PAG, and isobutene gas was produced in the polymer matrix. The resulting polymer foamed with the gas had cell size and cell density ranging from 100 to 200 nm and from 1 × 10¹³ to 9 × 10¹³ cells/cm³, respectively. Several key parameters were found that would affect largely on the formation of the nanocellular structure, i.e., foaming time and temperature, UV dose, molecular weight of polymer.

The hydrogel grafted polyethylene terephthalate (PET) textiles were envisioned to have oil-repelling properties due to the synergistic of combining hydrophilic hydrogel onto PET textiles surfaces. In this work, PAAm hydrogels were grafted i.e. via immersion or dipping methods onto pristine (PPET) and alkaline treated (APET) PET textile surfaces using UV LED light source. The obtained samples were then characterized based on the degree of grafting (DG), Fourier transformed infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), surface wettability by contact angle and oil fouling test. APET was found to be more efficient for grafting compared to the PPET due to the surface modification made after the alkaline treatment. APET surface turned to be more hydrophilic than PPET due to the presence of hydroxyl group (-OH) as proven in the FTIR. In addition, the PAAm hydrogel was confirmed to be successfully grafted onto the APET textile via immersion or dipping methods with the optimum DG obtained was at 20 minutes of UV time. This finding has also proven the potential of UV LED as a promising technology to replace the conventional UVA for hydrogel curing. Higher DG was obtained for immersed grafting sample (PAAm-g-APET_imm; DG=160 wt%) when compared to the dipped sample (PAAm-g-APET_dip; DG=60 wt%) which indicates that higher mass fraction of PAAm could be attached to the surface of PAAm-g-APET_imm. Apart from that, PAAm-g-APET_imm shows lower water contact angle (WCA) with WCA=60.90° as compared to PAAm-g-APET_dip with WCA=83.15° which could be due to higher thickness of hydrophilic layer that resulted in slower rate of oil fouling performance. To summarize, the PAAm hydrogel grafted onto PET textiles were significantly improved and possessed excellent surface towards oil staining performance. By comparing both textile modifications, grafting via dipping was more preferable. Even though the DG obtained was slightly lower, its thin layer of hydrogel grafted on the APET textile surface was sufficient to de-stain oil from the textile surface at a faster rate (~0.60-0.70 seconds). To some extent; the hydrogel modified textiles via UV LED curing has bright vision in the near future as promising tools for oil/water separation.

This paper presents the effect of UV-LED and UV-mercury as the light source toward curing behaviour of urethane acrylate coating. The UV-curable coating was prepared based on aliphatic urethane acrylate oligomer, 2-ethylhexyl acrylate (2-EHA), methyl methacrylate (MMA), trimethylolpropane triacrylate (TMPTA), and commercial photoinitiator. The effect of irradiation time on curing behaviour was investigated using Fourier Transform Infra-Red (FTIR) and the percentage of C=C conversion was calculated. From the ATR-FTIR spectra, the C=C absorption peak at 810 cm^－1 and 1635 cm^－1 was found to be decreased after UV irradiation, indicated the proceeding of the polymerisation reaction. In term of C=C conversion, UV-LED irradiation showed better results with 97-99% than UV-mercury irradiation which is 86-96%. It was also observed that the tackiness of the coating reduced via UV-LED irradiation, suggesting higher conversion of monomers. Gel fraction of the coating also measured and higher gel fraction values, > 98% in this study was associated with higher cross-linking density. The results of this study depicted that UV-LED is a viable alternative to replace UV-mercury-based lamp in the coating industry.

Extreme ultraviolet (EUV) lithography is a prominent candidate for printing under 10nm half pitch patterns. Recently, we have developed metal organic cluster resists possessing higher EUV absorbing elements and controlled molecular size and distribution. Here, we report lithographic performance of zirconium organic cluster and zinc organic luster resists. EUV exposure results for the zinc organic cluster resists on different underlayers are also discussed.

Perovskite solar cells (PSCs) have shown a significant improvement in power conversion efficiency (PCE) in the last few years. However, instability of PSCs is still a barrier for successful industrialization. In particular, spiro-OMeTAD with additives, despite a popular choice for hole transport material (HTM) in PSCs, is one of the causes for device thermal instability. In this work, one of additives in HTM, 4-tert-butylpyridine (tBP) is proved to be a factor of device instability under thermal treatment. Simple solution engineering which excludes the use of tBP in the HTM results in better device stability. The origin of thermal stability improvement shown in this work is attributed to the suppression of morphological change of HTM. Further researches towards thermal stability of perovskite material and dopant-free HTM should be essential since tBP removal was not able to solve the thermal stability issue.

The development of new organic semiconductors for organic solar cell applications continues to be as an important subject. We recently developed fluorinated naphthobisthiadiazole (FNTz) for use as a new electron-accepting unit for nonfullerene acceptors. In this letter we report on the design and synthesis of a new electron-transporting π-conjugated polymer containing FNTz and an investigation of the influence of the FNTz unit on the properties and photovoltaic characteristics of the molecule. The introduction of the FNTz unit led to red-shifted absorption and low-lying frontier orbital energy levels, compared to those of NTz. Organic solar cells based on the FNTz–containing polymer, when combined with poly(3-hexylthiophene) as a donor showed an improved power conversion efficiency of 1.13%. These results indicate that FNTz could be an effective electron-accepting unit for electron-transporting polymer.

High efficiency lead halide perovskite solar cells employ spiro-OMeTAD or PTAA as a hole transporting material. This type of hole conductor requires dopants mainly to improve hole mobility. Although such doping has improved solar cell performance, in particular open circuit photovoltage and fill factor, the mechanism of the improvement has rarely been elucidated. Here, we demonstrate influence of dopants in spiro-OMeTAD on interfacial charge separation and recombination processes for a MAPbI₃ perovskite film sandwiched by an m-TiO₂ film and a spiro-OMeTAD layer by employing a series of transient absorption spectroscopies. The interfacial charge recombination time was significantly retarded by the doping. We propose that the retardation of the charge recombination originates from relatively longer distance of holes from the perovskite/spiro-OMeTAD interface owing to the increased hole mobility by the doping, potentially increasing Voc of the solar cell.

From the environmental and economical aspects, the development of less-toxic lead-free perovskite is an imperative challenge for next generation photovoltaics. Although bismuth-based dimer perovskite (A₃B₂X₉) and double perovskite (A₂BB’X₆) (A = cation, B = Bi, B’ = Ag, X = halogen) have been considered as the plausible candidates, their power conversion efficiencies (PCE) are still low (～2.2%). In this work, we comparatively evaluated the photoconductivity and charge carrier transfer to electron/hole transport layer (ETL/HTL) in A₃B₂X₉ and A₂BB’X₆ by time-resolved microwave conductivity (TRMC). In contrast to A₃B₂X₉, A₂BB’X₆ showed much higher photoconductivity and charge transfer efficiency to ETL/HTL. This result is consistent with the PCEs of our photovoltaic devices, in which the double perovskite of Cs₂AgBiBr₆ exhibited greatly improved fill factor and one order larger photocurrent density than dimer perovskites (Cs₃Bi₂I₉, MA₃Bi₂I₉, and FA₃Bi₂I₉; MA = methlyammonium cation, FA = formamidinium cation). Our results provide an insight into the key role of photoactive layer and charge transfer process.

The detailed morphological studies of poly(3-hexylthiophene)(P3HT)-b-polyisobutylene(PIB)-b-P3HT:P3HT blend thin films by grazing incidence X-ray scattering (GIXS) were reported. The results of GIXS experiments indicated the formation of phase separation between P3HT and PIB domains even after blending the P3HT homopolymer below 30 wt%. The change in d-spacing values of the phase-separated under strains was suppressed by increasing the weight ratio of the P3HT homopolymer, probably due to the disruption of the microphase separation. The blending the P3HT homopolymer induced the edge-on orientation during the strain process below 75%, probably by improving the interaction between P3HT domains in the blend thin films. The OPV characteristics were obtained with the device structure of ITO/PEDOT:PSS/P3HT-b-PIB-b-P3HT:P3HT:PC₆₁BM/Ca/Al, significantly improving the J_SC and FF values by increasing the P3HT homopolymer weight ratio. The excellent elongation behavior of P3HT-b-PIB-b-P3HT:P3HT blend bulk films (P3HT < 30 wt%) could be achieved, probably due to the formation of microphase separation between semi-crystalline P3HT and rubbery PIB domains.

We have developed an inductively-coupled plasma-reactive ion etching system (ICP-RIE) as a human-size tool of Minimal Fab for processing a half-inch wafer. The etching system has performed a Bosch etching process with a short switching cycle in a small chamber with a volume of 1/4 L. For the small chamber, we use a frequency of 100 MHz that is higher than the typical frequency of 13.56 MHz. The power consumption at 100 MHz is only ～ 40W. The Si etching rate of the Bosch process is ～ 2.5 μm/min. Moreover, residence times of deposition gas (C₄F8) and etching gas (SF6) are estimated to be ～ 0.2 second, and actually waiting times until feeding one of the gases into the chamber after the stop feeding the other gas are nominally set to be zero. The resultant Bosch cycle time of the alternative feeds of the two gases is only 2 sec. For the high-speed Bosch cycle of 2 sec, the resultant etching sidewall of Si structure becomes a scallop-less straight wall.

Imprint lithography is an effective and well known technique for replication of nano-scale features. For the purpose of semiconductor device fabrication, nanoimprint lithography (NIL) manufacturing equipment utilizes a patterning technology that involves the field-by-field deposition and exposure of a low viscosity resist deposited by jetting technology onto the substrate. In this paper we describe the latest performance update of the equipment, and to discuss the alignment system and overlay methods needed to yield advanced semiconductor devices. Throughputs of up to 90 wafers per hour have been achieved using a cluster system approach. On tests wafers a mix and match overlay of 3.2 nm is demonstrated. Additionally, a Drop Pattern Compensation (DPC) method is introduced as an additional means for improving overlay. Finally, to address cost of ownership, a mask lifetime of over 300 wafer lots has been demonstrated.