Investigation of the Possibility to Use Ge p-i-n Photodiodes in Infrared SPR Sensors

Considered in this work are the possibility and advantages of applying a Ge photodiode to measure the surface plasmon resonance (SPR) in the near infrared range (IR). The investigations were performed using the prototype of IR SPR refractometer that operates with two fixed wavelengths (1310 and 1552 nm) for excitation of surface plasmons in a thin gold film in the Kretschmann optical scheme. The obtained results of experiments enabled us to draw the conclusion that application of the Ge photodiode in the SPR sensor at the wavelength 1.5 µm allows increasing the sensitivity and response magnitude as well as widening the dynamic range of this sensor device.

Формирование наночастиц Au и особенности травления подложки Si после облучения атомарными и молекулярными ионами

Formation of metal nanoparticles on silicon substrate by thin gold film irradiation with accelerated atomic and molecular ions is shown. Structures obtained were etched by metal-assisted catalytic chemical technique to get porous silicon structure. Size of gold nanoparticles and the structure of porous siliconstrongly depend on kind of incident species and ion dose. A local increase in the energy release density at the target surface that takes place during molecular ion bombardment significantly reduce the doses required for the formation of predetermined film morphology and the distribution of nanoparticles on the surface, while at the same time molecules exhibit lower radiation effect on the substrate. Luminescent properties of porous silicon do not depend on the kind of ion used, and can be tuned by composition of an etching solution

Enhanced terahertz conductivity in ultra-thin gold film deposited onto (3-mercaptopropyl) trimethoxysilane (MPTMS)-coated Si substrates

Various material properties change considerably when material is thinned down to nanometer thicknesses. Accordingly, researchers have been trying to obtain homogeneous thin films with nanometer thickness but depositing homogeneous few nanometers thick gold film is challenging as it tends to form islands rather than homogenous film. Recently, studies have revealed that treating the substrate with an organic buffer, (3-mercaptopropyl) trimethoxysilane (MPTMS) enables deposition of ultra-thin gold film having thickness as low as 5 nm. Different aspects of MPTMS treatment for ultra-thin gold films like its effect on the structure and optical properties at visible wavelengths have been investigated. However, the effect of the MPTMS treatment on electrical conductivity of ultra-thin gold film at terahertz frequency remains unexplored. Here, we measure the complex conductivity of nanometer-thick gold films deposited onto an MPTMS-coated silicon substrate using terahertz time-domain spectroscopy. Following the MPTMS treatment of the substrate, the conductivity of the films was found to increase compared to those deposited onto uncoated substrate for gold films having the thickness less than 11 nm. We observed 5-fold enhancement in the conductivity for a 7 nm-thick gold film. We also demonstrate the fabrication of nanoslot-antenna arrays in 8.2-nm-thick gold films. The nanoslot-antenna with MPTMS coating has resonance at around 0.5 THz with an electric field enhancement of 44, whereas the nanoslot-antenna without MPTMS coating does not show resonant properties. Our results demonstrate that gold films deposited onto MPTMS-coated silicon substrates are promising advanced materials for fabricating ultra-thin terahertz plasmonic devices.

Study on a silver box unearthed from the Tang Dynasty (AD 618–907) tomb at Xiaolizhuang Site, Henan Province, China

Over the years, numerous gold and silver artifacts were excavated from tombs of the Tang Dynasty which gave evidence of the sophisticated metalworking techniques at that time. However, very few of them were studied and the manufacturing process was barely known. In this research, the microstructural analyses including microscopy and SEM–EDS were conducted on a delicate silver cosmetics box excavated from a Tang Dynasty tomb of Xiaolizhuang site. The silver artifact is made up of two symmetrical cambered pieces which were fabricated by alternating hammering and annealing. The shape and surface features were further modified through plastic forming. Afterwards, spinning technique was employed to ensure the interior surface is smooth and has consistent thickness. The surface of the silver box is fully decorated with multiple fine engraving including petals, fish-toe circles, flower pattern, twine pattern and the Tang grass pattern. According to the overlapping status of the notches, the patterns were processed in a certain order by using various gravers. The artifact was brought in its final appearance by gilding to form a thin gold film on the surface. These results overall reveal the sophisticated techniques applied in making the artifact and further enhance the understanding of metalworking practices in the Tang Dynasty.