*2.1. Materials*

Semicon p-type silicon wafers, 525 μm thick, of an <111> orientation, resistivity of 9–12 Ω·cm and dimensions of 15 × 15 × 0.5 mm<sup>3</sup> were used as substrates for FTIR *(Fourier Transform Infrared Spectroscopy*), XPS (*X-ray Photoelectron Spectroscopy*) and ellipsometric investigations.

Boron-silicon glass slides and fused silica plates of the dimensions 25 × 25 × 0.2 mm<sup>3</sup> 300–700 were used as substrates for UV-Vis (*Ultraviolet-Visible*), AFM (*Atomic Force Microscopy*) and SEM (*Scanning Electron Microscopy*) studies as well as for preparation of the "cold mirror" type of interference filter.

Prior to deposition, all substrates were subjected to ultrasonic rinsing in 99.8% methanol for 10 min in order to remove surface fat and microparticle contamination.

As a source of silicon:


As working gases:


#### *2.2. Deposition of the Coatings*

In the present work, an RF PE CVD reactor (a schematic representation of which is given in reference [26]) was used for the purpose of deposition of SiNC, SiNOC and SiOC films. The stainless-steel jar-type deposition chamber of this reactor is furnished with the RF electrode, with the counter-electrode being the entire jar. The chamber volume amounts to approximately 50 dm3. Working gases and precursor vapors were introduced to the reactor through separate lines terminated with shower-type distributors. Organosilicon compound container as well as (ca. 40 cm long) vapor supply lines were heated, with the former remaining at 303 K and the latter being subjected to a temperature gradient of 308 hw–413 K, in order to avoid condensation. Precursor flow rate was constant, and amounted to 6 sccm (standard cubic centimeters per minute). Initial pressure was equal 0.5 Pa and the self-bias voltage amounted to −880 V. Both the role and the amount of self-bias voltage were optimized as described in one of our earlier works [26]. The most important deposition process operational parameters are presented in Table 1, below.


**Table 1.** The settings of deposition parameters.

The coatings were deposited in the working atmosphere of oxygen and nitrogen with the total pressure being set constant. For that purpose, an especially designed valve system was constructed, allowing for pressure equalization in all the reactor elements. This solution is a subject of national patent procedure of several PL424592 (A1). With the help of that valve system, the reactor pressure was maintained at 20 Pa, independent of the composition of the working gas, which was changed between 100% O2 and 100% N2 at a constant total flow rate of 20 sccm. Each gas flow rate was independently regulated by a separate flow rate controller. Changes in working gas composition were performed step-wise, with the steps being not longer than 5 s, which ensured a smooth flow regulation. In the direction from oxide to nitride, deposition time amounted to 240 s, while that in the opposite direction was equal 60 s. Flow changes of working gas components were controlled with the MONITOR software. The acronyms of the samples used in this work are presented in Table 2, below.

**Table 2.** The acronyms of the samples used in this work.

