High-Throughput Direct Writing of Metallic Micro- and Nano-Structures by Focused Ga<sup>+</sup> Beam Irradiation of Palladium Acetate Films

Titanium dioxide (TiO2) is an attractive material for planar photonics; thus, the fabrication of TiO2 micro- and nanostructures has been a topic of many reports in recent years. In this work, we have presented systematic studies on focused electron beam (e-beam) micro- and nanopatterning of sol–gel-derived layers based on different alkoxide precursors of TiO2 stabilized with benzoylacetone (BzAc). The e-beam method is a flexible high-resolution technique, whereas the use of the sol–gel process, which utilizes precursors of titania in the condensed phase, enables lower electron doses in comparison to gas-phase precursors from injection systems. As the sol–gel process is relatively complex, we analyzed the effect of different process parameters on the patterning. It has given us insight into the phenomena related to the e-beam irradiation of sol–gel-derived layers based on titanium alkoxide precursors. We have examined patterned films using scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, ellipsometry, and profilometry. We have shown that the role of the alkoxy chain length in the processing of sol–gel-derived layers is more significant in the case of alcohol solvents than titania precursors. Moreover, high-resolution periodic nanostructures with steep sidewalls and high aspect ratio can be patterned, especially when the molar ratio of BzAc to titanium alkoxide in sol is increased from 1:1 to 2:1. Although the patterned films have a high concentration of carbon, it can be completely removed by annealing at 500 °C. This heat treatment leads to an increase in the refractive index from 1.59 to 2.11 (at the wavelength of 632.8 nm), but the patterned film turns polycrystalline in the nanoscale, showing the anatase phase of TiO2. The obtained results indicate that the investigated patterning method can be potentially applied for direct writing of planar photonic components with nanoscale features such as grating couplers for sensors. Nevertheless, the fabrication of high-quality TiO2 structures still needs optimization.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Focused Electron Beam Micro- and Nanopatterning of Thin Films Derived from Sol–Gels Based on TiO₂ Precursors for Planar Photonics

Rola,

Duda,

Gorantla

et al. 2024

“…Sacrificing the high enhancement, but greatly benefiting in repeatability, surfaces with immobilized noble metal nanoparticles, − or metal-capped structured arrays and nanowires, Au-coated flexible polymer “fingers”, are increasingly used in laboratory practice. However, their fabrication techniques, such as electron-beam lithography, − focused ion-beam lithography, and metal-assisted chemical etching, are often multistep, complex, and not cost-efficient, leaving room for the development of new approaches for cheap and scalable SERS substrate production.…”

Section: Introductionmentioning

confidence: 99%

Stable and Reusable Lace-like Black Silicon Nanostructures Coated with Nanometer-Thick Gold Films for SERS-Based Sensing

Golubewa

Klimovich

Timoshchenko

et al. 2023

We propose a simple, fast, and low-cost method for producing Aucoated black Si-based SERS-active substrates with a proven enhancement factor of 10 6 . Room temperature reactive ion etching of silicon wafer followed by nanometer-thin gold sputtering allows the formation of a highly developed lacetype Si surface covered with homogeneously distributed gold islands. The mosaic structure of deposited gold allows the use of Au-uncovered Si domains for Raman peak intensity normalization. The fabricated SERS substrates have prominent uniformity (with less than 6% SERS signal variations over large areas, 100 × 100 μm 2 ). It has been found that the storage of SERS-active substrates in an ambient environment reduces the SERS signal by less than 3% in 1 month and not more than 40% in 20 months. We showed that Au-coated black Si-based SERS-active substrates can be reused after oxygen plasma cleaning and developed relevant protocols for removing covalently bonded and electrostatically attached molecules. Experiments revealed that the Raman signal of 4-MBA molecules covalently bonded to the Au coating measured after the 10th cycle was just 4 times lower than that observed for the virgin substrate. A case study of the reusability of the black Si-based substrate was conducted for the subsequent detection of 10 −5 M doxorubicin, a widely used anticancer drug, after the reuse cycle. The obtained SERS spectra of doxorubicin were highly reproducible. We demonstrated that the fabricated substrate permits not only qualitative but also quantitative monitoring of analytes and is suitable for the determination of concentrations of doxorubicin in the range of 10 −9 −10 −4 M. Reusable, stable, reliable, durable, low-cost Au-coated black Si-based SERS-active substrates are promising tools for routine laboratory research in different areas of science and healthcare.

“…To address these issues, organometallic compounds have been applied as negative resist, − especially in the preparation of NRs with zinc acetate (Zn(OAc) 2 ) as the main component of the precursor solutions. However, existing methods to decompose zinc acetate have certain limitations.…”

Section: Introductionmentioning

confidence: 99%

Growth of Vertical ZnO Nanorods from Patterned Films via Decomposition of Zinc Acetate by Focused Ion Beam: Implication for UV Detection

Yang,

Meng,

Liu

et al. 2023

Zinc oxide (ZnO) nanorod arrays have a wide range of applications. Controlling the position of the seed layers (ZnO films) and the nanorod morphology plays an essential role in the fabrication of the sensors and the fulfilment of specific sensing properties, while the patterning of seed layers and controlling the NR morphology have mostly been studied separately. In this study, a focused ion beam was employed to decompose spin-coated zinc acetate films for the precise positioning of the seed layers. The resulting ZnO films were used to hydrothermally grow vertical ZnO NRs that process a high responsivity of 1.24 × 106 A/W at a bias voltage of 5 V. Moreover, this approach provides the following advantages: (1) the carbon to zinc ratio of the zinc acetate film decreased from 4:1 to 1:18.9 after irradiation, demonstrating the efficient decomposition; (2) a patterned ZnO film can be obtained with a low irradiation dose of 1000 μC/cm2; and (3) the seed layer can be utilized directly for vertical nanorod growth without annealing. The morphology of NRs is characterized, and the nanorods grown on seed layers under different treatment conditions had different X-ray diffraction (XRD) peak patterns. Furthermore, the UV–vis absorption spectra of the nanorods were measured. Finally, we examined the rapid patterning of the ZnO thin films. We propose a simple and efficient approach for the decomposition of zinc acetate into patterned ZnO; this provides an integrated solution for ZnO film positioning and the vertical growth of ZnO NRs, which could also offer an approach and inspiration for ultraviolet (UV) detection and ideas for the localized growth of other ZnO nanomaterials.