Deposition of yttria-stabilized zirconia thin films by high power impulse magnetron sputtering and pulsed magnetron sputtering

Abstract

Yttria-stabilized zirconia (YSZ) thin films were reactively sputter-deposited by high power impulse magnetron sputtering (HiPIMS) and pulsed direct current magnetron sputtering (DCMS). The use of substrate bias voltage was studied in both modes of deposition as a process parameter to promote the growth of dense and less columnar films. Films were deposited on both Si(100) and NiO-YSZ fuel cell anodes. The texture, morphology and composition of the deposited films were investigated with regard to their application as thin electrolytes for solid oxide fuel cells (SOFCs). Independent of the deposition mode the films were found to be stoichiometric. The application of substrate bias voltage had opposite effects on texture and crystallinity of films deposited by pulsed DCMS and HiPIMS. Films deposited by pulsed DCMS became highly crystalline and <220> textured at high bias voltage whereas bias applied to HiPIMS deposited films disrupted crystal growth leading to deterioration of crystallinity. Comparing film morphology, it was found that pulsed DCMS films were columnar and contained voids regardless of the applied substrate bias. When depositing by HiPIMS a window of operation at a bias voltage of -25 V to -50 V was found in which it is possible to deposit non-columnar thin films without voids and cracks as desired for SOFC applications.

A review comparing cathodic arcs and high power impulse magnetron sputtering (HiPIMS)

“…Widely practiced for compound films, including nitrides [77,199,[291][292][293], carbides [294], oxides [277,[295][296][297][298][299][300][301][302], and more complex compounds [303,304]. [306].…”

Scale‐up of Solid Oxide Fuel Cells with Magnetron Sputtered Electrolyte

“…Typically, to make a thin film electrolyte on the sub‐micrometer scale, different solution‐based processes like metal‐organic deposition and spray pyrolysis , chemical and physical , vapor deposition methods are used. The solution‐based processes have problems associated with shrinkage that accompanies drying and sintering.…”

“…The largest size of single cells with the magnetron sputtered electrolyte, known from literature, is 5 × 5 cm 2 , . This cell's size is obviously insufficient for the manufacture and testing of SOFS stacks.…”

Magnetron deposition of yttria-stabilised zirconia electrolyte for solid oxide fuel cells

“…Most often to deposit YSZ electrolyte, sputtering in DC-pulsed mode is used. However, in the works of Sonderby et al [37,38], for depositing the YSZ electrolyte on NiO/YSZ anodes, high power impulse magnetron sputtering was used. HiPIMS utilizes extremely high power densities of the order of kW/cm 2 in short pulses of tens of microseconds at low duty cycle (on/off time ratio) of <10%.…”

“…Sonderby et al [37] compared the microstructure of YSZ electrolytes deposited on (5 × 5) cm 2 anode substrates by the DC-pulsed magnetron sputtering and HiPIMS methods at a bias voltage in the range of 0 to -75 V. It was concluded that in the case of DC-pulsed magnetron sputtering, an increase in the bias voltage does not lead to complete suppression of the columnar structure of the electrolyte, whereas at high power impulse magnetron sputtering with a bias voltage of -50 V the dense electrolyte films without a columnar structure are deposited ( Figure 3). The electrochemical characteristics of SOFC have not been studied in this work.…”