Reaktivní depozice vrstev Si-B-C-N pomocí kontinuálních a pulzních magnetronových výbojů

Ing. Pavel CALTA

Doctoral thesis

Reactive deposition of Si-B-C-N coatings using continuous and pulsed magnetron discharges

Abstract:

Zájem o nové kvaternární materiály SiBCN roste díky jejich vysokoteplotním vlastnostem a použití v nepříznivých podmínkách. Tvrdé (22-24 GPa) amorfní vrstvy SiBCN s vysokoteplotní stabilitou a oxidační odolností (nad 1500°C) byly deponovány na různé substráty (Si, SiC, WC-Co s vrstvou 250 nm TiN nebo CrN) pulzním magnetronovým naprašováním použitím terče B4C-Si (25:75 %) ve směsi Ar-N2 (50:50 %). Teplota substrátů byla 350 °C, celkový pracovní tlak 0,5 Pa a předpětí na substrátech -100 V nebo byly substráty na plovoucím potenciálu. Byl zjišťován vliv pulzního výboje na kvalitu vrstev, jejich vysokoteplotní vlastnosti a na adhezi vrstev k průmyslově zajímavým substrátům.

Abstract:

Novel quaternary SiBCN materials are becoming increasingly attractive because of their possible high-temperature and harsh-environment applications. Hard (22 - 24 GPa) amorphous Si-B-C-N coatings with high thermal stability and oxidation resistance (even above 1500 °C) were deposited on various substrates (Si, SiC, WC-Co and WC-Co with 250 nm TiN or CrN interlayers) by pulsed dc magnetron sputtering using a single B4C-Si (25:75 %) target in an Ar-N2 (50:50 %) gas mixture. The substrate temperature of 350 °C and the total pressure of 0.5 Pa were held constant during the depositions on the substrates at a floating potential or an rf induced bias of -100 V. A planar rectangular (127 x 254 mm2) unbalanced magnetron was driven by a pulsed dc power supply operating at the repetition frequency of 10 kHz and the average target power over a period of about 500 W with 50 % and 85 % duty cycles. Here, the aim was to avoid any discharge instabilities leading to possible defects in the coatings. Laser confocal scanning microscopy showed a very smooth surface morphology of the as-deposited coatings with an average roughness Ra = 6 nm determined over the surface area of 120×90 microns2. Prior to deposition, a modification of the substrate surfaces (etching, shallow implantation and ion mixing) was performed by pulsed magnetron sputtering of the B4C-Si target in Ar gas at the same pressure, the duty cycle of 20 % and the average target power over a period of about 250 W, the substrate temperature from 350 °C to 480 °C and the rf substrate bias of - 1300 V for 12 min to enhance adhesion of the deposited Si-B-C-N coatings to various substrates. The adhesion measurements were carried out by a scratch tester using a spherical diamond indenter with a tip radius of 200 mm and a linearly increasing normal load from 0 to 80 N. The critical load (Lc) was revealed by optical microscopy and confirmed by a sharp change in the slope of the corresponding dependences measured for the friction coefficient. A substantial increase in the critical load (from 16 to 70 N for the WC-Co substrate) caused by the substrate surface modification was proved.

Keywords

vrstva SiBCN, magnetronové naprašování, vysokotepltoní stabilita, oxidační odolnost

Language used: Czech

Date on which the thesis was submitted / produced: 2. 5. 2011

Identifier: 23503

Thesis defence

University of West Bohemia

Faculty of Applied Sciences

Doctoral programme / field:
Applied Sciences and Computer Engineering / Plasma Physics and Physics of Thin Films