arXiv subjects

Arnold Müller

Publications and source records attributed to Arnold Müller.

6 recordsLinked to original sources

arXiv2026

Accelerated development of amorphous InZnO thin films as transparent conductive Cu diffusion barriers

In light of the increasing supply chain concerns regarding silver for solar cell metallization, the replacement of the silver contacts by copper is desirable. As copper diffuses readily in silicon, deposition of an additional diffusion barrier to protect the respective absorber material stacks is required. We investigate multifunctional layers of transparent conductive oxides (TCOs) from the In-Zn-O system to serve as front electrode and Cu diffusion barrier coating, focusing on purely amorphous layers without grain boundaries to impede copper diffusion. We employ a 2D combinatorial approach to simultaneously screen the Zn/(In+Zn) ratio and the oxygen content in a single materials library deposited by magnetron sputtering without intentional substrate heating. Cu diffusion barrier performance was evaluated by depositing Cu on top of intentionally ultrathin In-Zn-O libraries of 7 nm on silicon wafers and annealing them at temperatures of 200-450°C. Both the formation of copper silicides, as well as the silicon photoluminescence signal were monitored. The first was detected only after the crystallization of the In-Zn-O films and required annealing temperatures of 450°C and above. Even for extended dwell times of 20 h at a relevant process temperature of 200°C, we find no evidence of Cu ingress for most of our fabricated In-Zn-O compositions, whereas Si/Cu stacks without In-Zn-O barriers showed a reduction of their photo-luminescence intensity already after less than 1 h. These results suggest thin amorphous In-Zn-O films with an optimal Zn/(In+Zn) ratio of ~0.12 and intermediate oxygen deficiency as effective transparent conductive Cu diffusion barriers for solar cell applications.

cond-mat.mtrl-sci↗

arXiv2025

In situ impedance spectroscopy tests of Li$_{4-x}$Ge$_{1-x}$P$_x$O$_4$ as potential solid state electrolyte for Micro Li ion Batteries

Lithium-ion batteries employing solid-state electrolytes (SSEs) are emerging as a safer and more compact alternative to conventional batteries using liquid electrolytes, especially for miniaturized energy storage systems. However, the industry-standard SSE, LiPON, imposes limitations due to its incompatibility with high-temperature processing. In this study, we investigate Li$_{4-x}$Ge$_{1-x}$P$_x$O$_4$ (LGPO), a LISICON-type oxide, as a promising alternative thin-film SSE. LGPO thin films are fabricated using pulsed laser deposition under four distinct deposition conditions, with in situ impedance spectroscopy enabling precise conductivity measurements without ambient exposure. We systematically correlate deposition temperature, background pressure, chemical composition, crystallinity, and morphology with ionic transport properties. Polycrystalline LGPO films grown at high temperature (535 $^\circ$C) and low oxygen pressure (0.01 mbar) exhibited the highest room-temperature ionic conductivity ($\sim 1.2 \times 10^{-5}$ S cm$^{-1}$), exceeding that of LiPON by an order of magnitude, with an activation energy of 0.46 eV. In contrast, amorphous films show significantly lower conductivity ($\sim 5.2 \times 10^{-8}$ S cm$^{-1}$) and higher activation energy (0.72 eV). The results reveal that crystallinity, chemical composition, and grain boundary density critically affect ion transport, highlighting the importance of microstructural control. This work establishes LGPO as a viable, high-performance oxide SSE compatible with high-temperature processing for next-generation microbattery architectures.

cond-mat.mtrl-sci↗

arXiv2025

Accelerating the development of oxynitride thin films: A combinatorial investigation of the Al-Si-O-N system

Oxynitrides are used in a variety of applications including photocatalysts, high-k dielectrics or wear-resistant coatings and often show intriguing multi-functionality. To accelerate the co-optimization of the relevant material properties of these compositionally complex oxynitride systems, high-throughput synthesis and characterization methods are desirable. In the present work, three approaches were investigated to obtain orthogonal anion and cation gradients on the same substrate by magnetron sputtering. The different approaches included varying positions of the local reactive gas inlets and different combinations of target materials. The best performing approach was applied to screen a large two-dimensional area of the quaternary phase space within the Al-Si-O-N system. This material system is a promising candidate for transparent protective coatings with variable refractive indices. With only five depositions of combinatorial libraries, an anion composition range of 2-46% O/(N+O) and a cation composition range of 4-44% Si/(Al+Si) is covered. For lower oxygen and silicon contents, a region with hardness of up to 25 GPa is observed, where the material exhibits either wurtzite AlN or a composite microstructure. By increasing the deposition temperature to 400 °C, an extension of this region can be achieved. At higher oxygen and silicon contents, the structure of the samples is X-ray amorphous. In this structural region, an intimate correlation between hardness and refractive index is confirmed. The results of this study introduce a practical approach to perform high-throughput development of mixed anion materials, which is transferable to many materials systems and applications.

cond-mat.mtrl-sci↗

arXiv2024

Physical Properties and Thermal Stability of Zirconium Platinum Nitride Thin Films

Ternary transition metal nitrides (TMNs) promise to significantly expand the material design space by opening new functionality and enhancing existing properties. However, most systems have only been investigated computationally and limited understanding of their stabilizing mechanisms restricts translation to experimental synthesis. To better elucidate key factors in designing ternary TMNs, we experimentally fabricate and analyze the physical properties of the ternary Zr-Pt-N system. Structural analysis and DFT modeling demonstrate that Pt substitutes nitrogen on the non-metallic sublattice, which destabilizes the rock-salt structure and forms a complex cubic phase. We also show insolubility of Pt in the Zr-Pt-N at 45 at % with the formation of a secondary Pt-rich phase. The measured reduced plasma frequency, decrease in resistivity, and decrease in hardness reflect a dominance of metallic behavior in bonding. Contrary to previous computational predictions, Zr-Pt-N films are shown to be metastable systems where even low Pt concentrations (1%) facilitate a solid reaction with the Si-substrate, that is inaccessible in ZrN films.

cond-mat.mtrl-sci↗

arXiv2023

Smart sensing of the multifunctional properties of magnetron sputtered $MoS_2$ across the amorphous-crystalline transition

Molybdenum disulfide, $MoS_2$, is a next-generation semiconductor and is frequently integrated into emergent optoelectronic technologies based on two-dimensional materials. Here, we present a method that provides direct optical feedback on the thickness and crystallinity of sputter-deposited $MoS_2$ down to the few-layer regime. This smart sensing enables tracking the material's functional properties, such as excitonic response, sheet resistance, and hardness across the amorphous-crystalline transition. To illustrate the potential of such feedback-controlled fabrication, we realized $MoS_2$-based hyperbolic metamaterials (HMM) with controllable optical topological transitions and hardness.

cond-mat.mtrl-sci↗

arXiv2023

Development of Nb-GaAs based superconductor semiconductor hybrid platform by combining in-situ dc magnetron sputtering and molecular beam epitaxy

We present Nb thin films deposited in-situ on GaAs by combining molecular beam epitaxy and magnetron sputtering within an ultra-high vacuum cluster. Nb films deposited at varying power, and a reference film from a commercial system, are compared. The results show clear variation between the in-situ and ex-situ deposition which we relate to differences in magnetron sputtering conditions and chamber geometry. The Nb films have critical temperatures of around $9 \textrm{K}$. and critical perpendicular magnetic fields of up to $B_{c2} = 1.4 \textrm{T}$ at $4.2 \textrm{K}$. From STEM images of the GaAs-Nb interface we find the formation of an amorphous interlayer between the GaAs and the Nb for both the ex-situ and in-situ deposited material.

cond-mat.mtrl-sci↗