Carbon-based materials have been studied for their antimicrobial properties. Previously, most antimicrobial studies are investigated with suspended nanoparticles in a liquid medium. Most works are often carried out with highly ordered pyrolytic graphite. These materials are expensive and are not viable for mass use on high-touch surfaces. Additionally, highly antimicrobial silver nanoparticles are often incorporated onto substrates by chemical reduction. At times, harmful chemicals are used. In this work, low-cost graphite pencils are mechanically exfoliated and transferred onto Si substrates. The sparsely-covered graphite flakes are treated by either plasma O2or UV irradiation. Subsequently, Ag is photo reduced in the presence of UV onto selected graphite flake samples. It is found that graphite flake surface topography and defects are dependent on the treatment process. High surface roughness and (defects density,ID/IG) are induced by plasma O2follows by UV and pristine graphite flake as follows: 6.45 nm (0.62), 4.96 nm (0.5), 3.79 nm (0.47). Antimicrobial tests withE. colireveal high killing efficiency by photoreduced Ag-on-graphite flake. The reversible effect of Ag leaching can be compensated by repeating the photoreduction process. This work proposes that UV treatment is a promising technique over that of plasma O2in view that the latter treated surface could repel bacteria resulting in lower bacteria-killing efficiency.
Carbon nanotubes (CNTs) have, over the years, been used in research as a promising material in electronics as a thermal interface material and as interconnects amongst other applications. However, there exist several issues preventing the widespread integration of CNTs onto device applications, e.g., high growth temperature and interfacial resistance. To overcome these issues, a complementary metal oxide semiconductor (CMOS)-compatible CNT array transfer method that electrically connects the CNT arrays to target device substrates was developed. The method separates the CNT growth and preparation steps from the target substrate. Utilizing an alignment tool with the capabilities of thermocompression enables a highly accurate transfer of CNT arrays onto designated areas with desired patterns. With this transfer process as a starting point, improvement pointers are also discussed in this paper to further improve the quality of the transferred CNTs.
We introduced photon-trapping microstructures into GeSn-based photodetectors for the first time, and achieved high-efficiency photo detection at 2 µm with a responsivity of 0.11 A/W. The demonstration was realized by a GeSn/Ge multiple-quantum-well (MQW) p-i-n photodiode on a GeOI architecture. Compared with the non-photon-trapping counterparts, the patterning and etching of photon-trapping microstructure can be processed in the same step with mesa structure at no additional cost. A four-fold enhancement of photo response was achieved at 2 µm. Although the incorporation of photo-trapping microstructure degrades the dark current density which increases from 31.5 to 45.2 mA/cm2 at -1 V, it benefits an improved 3-dB bandwidth of 2.7 GHz at bias voltage at -5 V. The optical performance of GeSn/Ge MQW photon-trapping photodetector manifests its great potential as a candidate for efficient 2 µm communication. Additionally, the underlying GeOI platform enables its feasibility of monolithic integration with other photonic components such as waveguide, modulator and (de)multiplexer for optoelectronic integrated circuits (OEICs) operating at 2 µm.
