Aligned silver nanorod (AgNR) array films were fabricated by oblique thermal evaporation. The substrate temperature during evaporation was varied from 10 to 100 °C using a home-built water cooling system. Deposition angle and substrate temperature were found to be the most important parameters for the morphology of fabricated films. Especially, it was found that there exists a critical temperature at ~90 °C for the formation of the AgNR array. The highest enhancement factor of the surface-enhanced Raman scattering (SERS), observed in the Ag films coated with benzenethiol monolayer, was ~6 × 107. Hot spots, excited in narrow gaps between nanorods, were attributed to the huge enhancement factor by our finite-difference time-domain (FDTD) simulation reflecting the real morphology.

ZnO nanomaterials are promising building blocks for an efficient UV photodetector; however, their slow sensing behavior and undesired response to visible light, which are attributed to surface defects, such as oxygen or zinc vacancies, are challenges that remain to be addressed. Here, we transformed the ZnO nanorod surface into a zeolitic imidazolate framework-8 (ZIF-8) to eliminate ZnO surface defects. Vertical-type photodetectors were fabricated incorporating a Schottky junction at the ZIF-8/gold (Au) top electrode and could respond to UV light with a rapid response and recovery (1–2 s) and demonstrated a UV-to-visible rejection ratio in the order of 10³, qualifying them as efficient visible-blind UV photodetectors. It is noteworthy that the ZIF-8 layer effectively separated the photogenerated electron–hole pairs, and thus reduced their recombination probability. The enhanced photodetector displayed excellent figures-of-merit: a responsivity of 291 A W⁻¹ and a detectivity of 5.9 × 10¹³ cm Hz^1/2 W⁻¹ under illumination at 295 nm.

Silver nanorod (AgNR) array substrates were fabricated using an oblique angle thermal evaporation technique; their long-term stability, surface uniformity and reproducibility, which are primary requirements for their widespread realistic application and commercialization, were assessed using surface-enhanced Raman scattering (SERS) spectroscopy. The nanorod surfaces were functionalized using a series of organic thiols, which range from hydrophilic to hydrophobic, to mimic various conditions that often arise during detection of hydrophilic/phobic analytes in a realistic application field. A group of these functionalized substrates was stored in ambient laboratory atmosphere; another in light minimized, moisture-free vacuum; while another was stowed carefully and neatly in water to mimic realistic conditions. The effects of these storing conditions were studied. A surfactant was added to the water to maintain consistent surface wetting in the third group. SERS spectra of nanorod substrates prior to functionalization were also recorded to investigate the effect of adventitious carbonaceous contaminants. A meticulous systematic study on the reproducibility of SERS signals was carried out: spot-to-spot, substrate-to-substrate, batch-to-batch, day-to-day. The relative standard deviation (RSD) shown by the SERS signals acquired from various spots of a single substrate was less than 3%, which is very similar to the only account reported so far, in which RSD is reported as 2%. The wetting behavior of these thiol functionalized AgNR substrates are investigated using static contact angle measurements. The functionalized substrates have exhibited excellent long-standing stability over a period of six months when stored appropriately; hence, they are highly suitable for mass production towards realistic application.

Continuous tuning of terahertz waves was demonstrated with seamless change in grating period in a periodically poled stoichiometric lithium tantalite (SLT) crystal. The periodically poled fan-out structure allows wide tunability such as 610 GHz with the bandwidth as narrow as 17 GHz at a carrier frequency of 1.00 THz. Temperature-dependent measurements show a gradual intensity increase of the THz pulses as the temperature decreases. Furthermore, absorption and refractive index of SLT in the THz range were estimated and compared with those of LiNbO3 (LN). The absorption coefficient of the LT crystal at ordinary wave was almost half of that in the LN crystal. SLT could be one of the powerful crystals for high-power THz generation with large optical aperture because of the fewer defects inside the crystal.

We report a new simple method for the signal enhancement of laser-induced breakdown spectroscopy using a pulsed buffer gas jet. The signal is enhanced up to more than 10 fold by using argon gas jets, which are injected through a pulsed nozzle onto the sample area to be analyzed. By synchronizing the buffer gas pulse with the laser pulse and optimizing the spatial arrangements between the gas jet and the sample surface, we have successfully exploited the useful properties of the buffer gas in open atmosphere. The signal-enhancement mechanism in our buffer gas jet has been discussed. Also, applications to various samples (metal, glass, and paper) have been demonstrated.