Sensing Element of the Surface Plasmon Sensor With Thermal Modification of the Structural Properties of the Polymer Substrate

Abstract

The development of an effective sensing element (ChE) sensor with a prism type of excitation (Kretchman configuration) of surface plasmon resonance (SPR) in a gold film and a mechanical survey of the angle of incidence of monochromatic light based on a polymer substrate is based on a combination of radiation binding schemes using a prism and a lattice to prevent losses in the active metal film. Replacing the glass substrate with a polymer one has reduced the cost of ChE, led to increased sensitivity and simplification of its manufacturing technology, which does not require the use of intermediate adhesion layers. Additionally, we applied a thermal method of modifying the optical and structural properties of the substrate – hot pressing of the matrix, which contained a periodically nanostructured surface relief in the form of a diffraction two-dimensional (2D) lattice. The original 2D lattice was recorded on photoresist-covered (Shepley 1805) glass plates using the method of two-beam interference (He-Cd laser, = 440 nm) at double exposure (time 2040 s, power 20 mW/cm2) of the sample with a rotation of 90. Characteristics of ChE on an optical polycarbonate substrate (d = 2.25 mm, n = 1.58 at ( = 650 nm) after hot pressing, which contained a flat and periodically nanostructured surface in the form of a diffraction 2D lattice, followed by the deposition of a thin (d 40 nm) layer of gold on them was examined using an atomic force microscope (AFM) and the device "Plasmon". AFM studies have shown that the technological technique used made it possible to obtain lateral-ordered structures in the form of pyramids with calculated parameters – a period of 422435 nm (spatial frequency of about 2350 lin/mm) and a relief depth of 7090 nm. However, the preservation of a wave-like relief (about 300 nm) on a flat part of the surface and double ray refraction of the polymer substrate, encourage optimization of the hot pressing process using the resulting matrix on polymer substrates of smaller thickness.