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Surface-enhanced Raman scattering (SERS) sensors have been extensively studied for ultrasensitive detection of diverse chemical or biological analytes. Facile fabrication of highly sensitive SERS substrates is believed to be of crucial importance in these analytical applications. In this regard, the preparation of 3-dimensional (3D) SERS substrates are explored via the incorporation of multilayered silver nanoparticles (AgNPs) into poly (oligo(ethylene glycol) methacrylate) (POEGMA) brushes by repeating the immersion-rinsing-drying steps for different lengths of time (i.e., the so-called in-stacking method). The POEGMA brushes of different chain lengths are synthesized by surface-initiated atom transfer radical polymerization (ATRP) with various reaction time. The resulting POEGMA/AgNP nanocomposites are characterized by FE-SEM, UV–vis and Raman spectroscopy. FE-SEM and UV–vis results indicate that the AgNPs are successfully incorporated into the POEGMA brushes with a 3D configuration. The nanocomposite films are employed as SERS substrates for the detection of a Raman reporter molecule (i.e., 4-aminothiophenol), giving rise to an enhancement factor of up to 1.29 × 107 and also having relatively good uniformity and reproducibility. The obtained 3D SERS substrates are also used for the detection of a typical gram-positive bacterium, Staphylococcus aureus. The limit of detection is found to be as low as ca. 8 CFU/mL.

Al2O3 films were deposited on n-type crystalline Si (c-Si) wafers by atomic layer deposition using Al(CH3)3 and H2O as precursors. Surface anti-reflectance and passivation performances were investigated. Average reflectances between 2.8 and 4.2% were obtained for Al2O3 coated textured Si with Al2O3 thickness ranged between 100 and 70 nm. Wide thickness window for low reflectance between 2.8 and 4.2% indicates its potential anti-reflectance applications. A high minor carrier lifetime of ～4.5 ms is obtained for n-type c-Si wafers passivated by 100 nm Al2O3 films, corresponding to an effective surface recombination velocity of ～4 cm/s. Wide annealing time window and wide annealing temperature window are addressed to obtain good passivation performances with high minor carrier lifetime >3 ms. The passivation performances are related to the released H atoms from Al–OH bonds and the formation of Al vacancies and O interstitials within Al2O3 films. Our results indicate that Al2O3 films show dual functions of anti-reflectance and surface passivation for photovoltaic applications.

W/Ti-doped diamond-like carbon (DLC) films were fabricated on Si substrates by co-sputtering W and Ti targets in methane and argon mixture atmosphere. The composition and the microstructure, internal stress, mechanical and tribological properties of the films were measured by X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), Raman spectra, BGS 6341 type film stress tester, nano-indentor and reciprocating ball-on-disc tester, respectively. The results indicated all films showed the amorphous structural characteristics and a constant thickness value of ∼600 nm (195 ± 15 nm Ti interlayer was designed in order to minimize the influence of Ti interlayer), and the Ti content increased from 0 to 34.5% as the W target current increased from 0 A to 14 A. As the W concentration increased from 0 to 2.6 at.%, the hardness increased to 12.7 GPa and the internal stress maintained at a low value and almost no change. Meanwhile, the friction coefficient and wear rate showed the lowest value (0.023 and 1.2 × 10 −8 mm 3 /N m, respectively). With the W content increased to 34.5 at.% further, the internal stress, friction coefficient and wear rate of film are dramatically increased.

Ti-doped diamond-like carbon (DLC) films were deposited on Si substrates at room temperature by magnetron sputtering Ti twin-target in methane and argon mixture atmosphere. The DLC films with different Ti concentrations were fabricated by varying the gas flow ratio of Ar/CH 4 . X-ray photoelectron spectroscopy (XPS), Raman spectra were used to analyze the composition and the microstructure of the films. The internal stress was calculated by using the Stoney equation, where the curvature of the film/substrate was measured by BGS 6341 type film stress tester. The mechanical and tribological properties of the films were systematically studied by the nano-indentor and reciprocating ball-on-disc tester, respectively. The Ti atomic concentration in the films increased from 0.41% to 8.2% as the Ar/CH 4 flow ratio increased from 60/190 to 140/110. The Ti atoms exist mainly in the form of metallic-like Ti rather than TiC when Ti concentration is 0.41%, confirmed by XPS analysis. As the Ti concentration rose to 6.7%, the Ti-DLC films transformed to composite DLC films with carbide phase embedded in the DLC matrix because of the formation of TiC. As a result, the hardness is decreased, while the stress is dramatically increased. The Ti-DLC films with 0.41% Ti doping showed a relatively high hardness (13.75 GPa), low stress (0.56 GPa), extremely low wear rate (∼10 −10 mm 3 /Nm) and low friction coefficient (0.05).

In this study, the specific DNA binding behavior of a water soluble C 60 derivative (C 60 DF) and redox-controlled hydrophilic-to-hydrophobic transformations of the relative C 60 DF monolayer on surfaces of glassy carbon electrode (GCE) have been demonstrated by using in situ electrochemical static contact angle analysis. The results illustrate that in situ electrochemical contact angle detection based on C 60 DF functional film can be utilized to sensitively probe some specific bio-molecular recognition like DNA interaction, which will provide the new strategy to develop the promising multi-signal responsive biosensors for relevant biological process.

Effects of variation of the oxygen partial pressure on the structural and optical properties of zinc oxide (ZnO) thin films prepared by reactive radio-frequency sputtering were investigated. Measurements by X-ray diffraction (XRD) and atomic force microscopy (AFM) indicated that the crystallinity and the surface morphology were sensitive to the oxygen partial pressure. The interfacial and optical properties of the targeted films were investigated by spectroscopic ellipsometry (SE) characterization. Based on Tauc-Lorentz (TL) model, the optical constants of ZnO films were tentatively extracted in the photon energy ranging from 1.5 to 6.0 eV. Analyses by XRD and SE revealed that the oxygen partial pressure had effect on the orientation of the ZnO films, the surface morphology, the packing density, and the interfacial layers. And the relationship between crystallinity and interfacial layer, as well as the relationship between surface roughness and packing density was discussed. All these had a significant impact on the optical properties illustrated by SE analysis.

High-k gate dielectric HfO2 thin films have been deposited on Si(1 0 0) by using plasma oxidation of sputtered metallic Hf thin films. The optical and electrical properties in relation to postdeposition annealing temperatures are investigated by spectroscopic ellipsometry (SE) and capacitance–voltage (C–V) characteristics in detail. X-ray diffraction (XRD) measurement shows that the as-deposited HfO2 films are basically amorphous. Based on a parameterized Tauc–Lorentz dispersion mode, excellent agreement has been found between the experimental and the simulated spectra, and the optical constants of the as-deposited and annealed films related to the annealing temperature are systematically extracted. Increases in the refractive index n and extinction coefficient k, with increasing annealing temperature are observed due to the formation of more closely packed thin films and the enhancement of scattering effect in the targeted HfO2 film. Change of the complex dielectric function and reduction of optical band gap with an increase in annealing temperature are discussed. The extracted direct band gap related to the structure varies from 5.77, 5.65, and 5.56 eV for the as-deposited and annealed thin films at 700 and 800 °C, respectively. It has been found from the C–V measurement the decrease of accumulation capacitance values upon annealing, which can be contributed to the growth of the interfacial layer with lower dielectric constant upon postannealing. The flat-band voltage shifts negatively due to positive charge generated during postannealing.