ICMCTF 2022 Session TS6-1-MoA: A Session to Acknowledge the Contributions of Joe Greene to the ASED, ICMCTF, AVS, and IUVSTA I

From its inception the benefits of sputter deposition have stemmed from the presence of plasma in the vicinity of the growing film. Bombardment with charged particles and energetic photons affect the substrate initial condition and all stages of film growth: nucleation, coalescence, competitive growth, and recrystallization. Measuring and controlling the fluxes and energy of the charged particles to the substrate is essential in achieving low-temperature growth of high-quality thin films. Under typical conditions during direct current magnetron sputtering (DCMS), the dominant ion species incident at the growth surface while sputtering with N₂/Ar gas mixtures optimized to obtain stoichiometric films is typically Ar⁺, while the ratio of the gas-ion flux to deposited metal flux J_i/J_Me ≤ 1. Densification is achieved by increasing the ion energy E_icommonly above 100 eV.[1] However, at higher ion energies, a steep price is extracted in the form of residual ion-induced compressive stress resulting from both recoil implantation of surface atoms and trapping of rare-gas ions in the lattice.An alternative approach is offered by strongly magnetically-unbalanced magnetron sputter deposition system, which allows ion-to-neutral flux ratios J_i/J_Me incident at the growing film to be varied over extremely wide ranges (up to > 20) at very low (below the lattice displacement threshold) ion energies (E_i ~ 10-20 eV).[2] Using high-flux low energy ion irradiation during deposition opens new kinetic pathways to independently control the texture (from completely 111 to completely 200) and microstructure (from underdense to fully dense) in transition metal (TM) nitride films grown on amorphous substrates as well as to achieve low-temperature epitaxy of refractory materials as well as of metastable alloys.

¹Petrov, I., Barna, P.B., Hultman, L., Greene, J.E. “Microstructural evolution during film growth” J. Vac. Sci. Technol. A,21 (2003) S117

²Greene, J.E., Sundgren, J.-E., Hultman, L., Petrov, I., Bergstrom, D.B., “Development of preferred orientation in polycrystalline TiN layers grown by ultrahigh vacuum reactive magnetron sputtering” Appl. Phys. Let. 67 (1995) 2928

Large resources are allocated world-wide to the green and digital transitions. It is also obvious that research and development in close cooperation between different sectors in society play a crucial role for this twin transition. Another important part to achieve the necessary change is access to advanced materials and new innovative processes for sustainable production of these materials.

In this talk we will describe a mapping study that have conducted of the Swedish broad field of advanced materials. The results show that the value added for Swedish Industries manufacturing advanced materials has continuously increased in the years studied (2011-2019). The field is also expected to globally grow with 5-10% annually. In addition to the industry sector Sweden has also a strong academic community, with several research groups at the international forefront to which Prof Joe Greene has contributed significantly. Based on the mapping conducted and other recent studies we will present recommendations aimed to further boost the field of advanced materials both in Sweden and elsewhere.For example, an increased coordination and cooperation between different sectors and disciplines as well as the use of computational and AI methods are necessary to reduced lead times for industrial impact and thus to industrial competitiveness in the field.

Magnetron sputter deposition of wear resistant hard coatings has found broad acceptance in many industrial applications serving e.g. the automotive, micro mashining, aeronautical and biomedical but also decorative industry. Perfect adhesion is a dominant precondition to meet reproducible production conditions. The paper discusses three types of substrate pretreatment prior to the actual film deposition: intensive Ar etching, metal ion etching by cathodic arc and HIPIMS technology respectively. Particular attention is paid to ion implantation during metal ion etching and the related epitaxy of the growing film. The resulting enhanced adhesion guarantees successful deposition of very hard and highly stressed e.g. TiAlN based superlattice coatings. The industrial realization of these methods of pretreatment is outlined by verification in a double (twin) cathode, combined cathodic arc/unbalanced magnetron and combined HIPIMS/unbalanced magnetron approaches. Two industrialized applications will be discussed in detail: (1) performance of superhard C-DLC coatings utilizing a five cathode batch type coater and (2) a simultaneous HIPIMS/UBM process depositing multilayer TiAlN/CrN coatingsproduced in a large scale multi cathode equipment.

Prof. Joe Greene has been an amazing mentor and teacher to me. Without his help and patience, I would never have succeeded as I have. My career is entirely thanks to Joe both during my graduate study and more importantly afterward. This talk briefly reviews how the synthesis and characterization of thin films, particularly by sputter deposition, as I learned from or with the support of Joe, has been applied to the full spectrum of materials applied to photovoltaics. Film materials studied include silicon, binary, and ternary materials and alloys. Novel dielectrics and contact materials have been developed including a metastable alloy of 30% Cu in bcc Mo. Characterization methods include microstructural, microchemical, and optoelectronic approaches. The results have been simulated with continuum elasticity, finite element, Monte Carlo, and density functional methods. The result is a detailed picture of how defects in semiconductors affect the performance of photovoltaics and how they are related to process conditions.

This talk will start with a brief history of how my background in thin films in Joe Greene’s group helped lead to a new approach to making practical solid oxide fuel cells (SOFCs). Although thin film vapor deposition techniques have not supplanted conventional ceramic processing of SOFCs, this talk will highlight vapor deposition methods likely to play an increasing role going forward. Recent developments in SOFCs and solid oxide electrolysis cells (SOECs) will be discussed. SOFCs are being increasingly applied for clean efficiency electrical generation, and produce highly concentrated CO₂ exhaust that is nearly sequestration-ready. SOECs have potential for highest efficiency conversion of renewable electricity to hydrogen and other renewable fuels. The devices can also be operated in both SOFC and SOEC modes to allow large-scale electrical energy storage – a key technology needed for enabling increased utilization of renewable wind and solar energy resources. Current research areas will be highlighted including improving device performance via reduced electrolyte thickness and highly-active nano-scale electrodes, and determining the mechanisms that limit device long-term stability.