**3. Use of near-field optical radiation focusing systems for the formation of submicron structures**

For the formation of nanoscale elements and structures, it was proposed to use near-field systems for focusing optical radiation. Lines with a width of 100 nm and a depth of 23 nm on the As2S3 film were recorded with a near-field probe with an aperture of 120 nm [23]. The main disadvantage of recording by this method is the low scanning speed (100 μm/s), which is due to the low efficiency of near-field probes based on conical optical fibers [2, 23]. The situation with the use of near-field probes for recording nanoscale elements on inorganic resistors may change with the creation of new more efficient probes for focusing laser radiation, in particular, microstrip pyramidal probes [2]. Images of different types of probes are shown in **Figure 3**.

The pyramid-type microstrip probe (PTMP) has a transparent pyramid-like core with a truncated corner. Metal strips coat two opposite sidewalls of the pyramid. The transparent body and two metal strips form a tapering microstrip line, similar to an

## *Recording of Micro/Nanosized Elements on Thin Films of Glassy Chalcogenide Semiconductors… DOI: http://dx.doi.org/10.5772/intechopen.102886*

ordinary microstrip line where two opposite sides of a dielectric rectangular slab are coated with metal films, as shown in **Figure 3**. The incident beam (either a focused beam or a dielectric waveguide mode) couples to the probe through its wide end, and propagates along the probe, reaching the narrow end that forms the aperture. The light passing through the narrow end interacts with the scanned sample. In farinfrared band metal strips can be represented with high accuracy as perfect conductors which can support quasi-TEM wave which has no cut-off size. The incident light should have electric field polarization orthogonal to the metal strips in order to excite the quasi-TEM mode that has no cut-off size. A microstrip probe has a significant advantage over a conventional near-field probe in far-field transmission coefficient, especially for the small aperture size (a < 100 nm) since it decreases with a decrease of the aperture size as a square of the aperture diameter.

The near-field recording mode can be realized using a nanoscale diaphragm on the surface of the photosensitive material. To record nanosized elements by diffractionlimited optical systems, it was previously proposed to place an additional masking layer on the photosensitive layer, which changes the refractive index at elevated temperatures, such as a semiconductor film with a large band gap [24]. For the formation of nanosized elements on a thin film of chalcogenide semiconductor, the technology of exposure through the diaphragm (mask) was implemented, created in a material with a nonlinear exposure characteristic (technology of high-resolution near-field storage Super-RENS). One of the main elements of the Super-RENS disk is a mask, which is used to form a light beam of minimum size to expose the photosensitive layer of chalcogenide semiconductor and separated from it by a protective layer of fixed thickness. The size of the optical spot created by the mask ultimately determines the size of the elements that are recorded in the media. The scheme of the Super-RENS recording method is shown in **Figure 4b** [25].

As the material of the diaphragm in the first experiments, thin antimony (Sb) films with a thickness of 15 nm were used, located between the protective layers of SiN (**Figure 4**) [25]. Significant optical nonlinearity of the thin antimony film located between the dielectric layers was detected. The change in transmittance was

#### **Figure 3.**

*(a) Most commonly used near-field tapered fiber probe, (b) near-field probe based on optical plasmon microstrip line (optical microstrip probe) [2].*

#### **Figure 4.** *(a) Conventional recording by NSOM, (b) super-RENS recording method [25].*

relatively significant and stable over time in the region with submicron dimensions. This recording technology made it possible to obtain fingerprints with linear dimensions of less than 100 nm on GeSbTe (GST) films [25]. In this structure, a thin film mask made of Sb was placed at a distance of the near field to the recording layer. It was found that the Sb2Te3 material can also be used as a masking layer. Using it, fingerprints with linear dimensions of 60 nm were recorded on a phase-transition material (GeSbTe). The dielectric material ZnS-SiO2 was used as a protective layer. The possibility of recording and reproducing elements with submicron dimensions is explained by the fact that in the process of recording and reading in the masking layer a small hole is formed, which functions as a local solid-state near-field lens [26].
