**2. Thermolithographic recording on chalcogenide films**

The diffraction nature of light prevents us from achieving sub-diffraction or nanometer resolution in an optical beam lithography system. It is necessary to develop special recording methods based on nonlinear interaction with photosensitive materials and conversion of the energy of incident radiation. The size of the elements

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

formed on the films of CVS was determined mainly by the resolution of the optical focusing system and the accuracy of the automatic focusing system. Previous analysis showed that microrelief structures on CVS films, the width of which is less than the resolution of diffraction-limited optics, can be created using the thermolithographic recording mode. Local heating of the film in the recording area by radiation with a non-uniform intensity distribution allows to reduce the size of the elements by selecting the recording mode [1, 7, 16, 17].

The recording of elements on photosensitive materials is carried out by a focused beam with a non-uniform intensity distribution (usually with a Gaussian intensity distribution) and this allows on a photosensitive material with a nonlinear exposure characteristic to record elements smaller than the diameter of the focused beam. One of the first experiments on recording on a semiconductor–metal material with a nonlinear exposure characteristic showed the possibility of reducing the size of the elements recorded by laser radiation by 2-3 times compared to the diameter of the laser beam measured at 1/e [18] formed on the films of chalcogenide vitreous semiconductors was determined mainly by the resolution of the optical focusing system and the accuracy of the automatic focusing system. Previous analysis showed that microrelief structures on CVS films, the width of which is less than the resolution of diffraction-limited optics, can be created using the thermolithographic recording mode. The local heating of the film in the recording area by radiation with a nonuniform intensity distribution allows to reduce the size of the elements by selecting the recording mode [19–21].

The minimum size of elements recorded on films of chalcogenide semiconductors with phase transitions by thermolithography was 100 nm [22]. The use of this technology was of interest for optical disc recording systems in CD, DVD, BD [7, 16], and the creation of diffractive optical elements [1]. Examples of thermolithographic recording on chalcogenide semiconductor films are shown in **Figure 1**. The recording beam diameter was 1.0 mm. Elements 0.7-0.8 μm wide were recorded [7, 15].

**Figure 1.** *The principle of the thermolithographic recording [21].*

#### **Figure 2.**

*(a) the relief microstructure on the positive inorganic photoresist GeSe2. [15]. (b) the relief microstructure on the negative inorganic resist As2S3 [7].*

Limitations of the thermolithographic recording mode are associated with a significant effect of fluctuations in the power of laser radiation on the size of the elements recorded on the nonlinear photosensitive material (**Figure 2**). The formation of nanoscale relief structures on thin films of CVS by diffraction-limited optical systems is problematic.
