Blog

To recognize the International Day of Women and Girls in Science and to celebrate all the amazing female customers in scientific research we work with, we reached out to Laura Wagner - a PhD researcher at TU Munich's Walter Schottky Institute (WSI) and Physics Department - to discuss her career path so far, the exciting research she is currently working on with her team, and what this day means to her a as a female scientist at an exciting point in her career.

The Kurt J. Lesker Company (KJLC) has supported organic electronics research since producing its first dedicated PVD tool series over 20 years ago, enabling many breakthrough results. Recently a team from CNR NANOTEC (Lecce, Italy) has reported a strategy to improve the stability and durability of flexible top-emitting organic light-emitting diodes in their paper "Flexible distributed Bragg reflectors as optical outcouplers for OLEDs based on a polymeric anode", with results obtained using both KJLC deposition tools and materials.

The ability to fabricate flexible nano-thin films is of great interest because of the increased demand for flexible technologies, a paradigm shift in high-tech and consumer electronics, already making significant technological and commercial impact by enabling the emergence of flexible photovoltaics, flexible electronics, flexible smart textiles and flexible displays. Flexible thin films are typically achieved by coating a given material onto a flexible substrate, via a chemical vapour deposition (CVD) process, where the coating ingredients are mostly organic materials and chemicals. Coating flexible thin films from inorganic materials such as metals, functional alloys, heterostructures, semiconductors, oxides and ceramics via solid state DC / RF plasma sputtering is less known, and it is unclear how the flexible substrate affects their properties. This project demonstrated the successful production of flexible magnetic thin films with excellent adhesion and mechanical robustness. Remarkably, the films maintained their structure, integrity and physical properties at any curvature bending applied to the flexible samples.

Electrons have two fundamental physical properties, their charge and spin. The charge of electrons has been discovered and carefully measured long time ago[1]. The utilization of the electron charge can be found in all electronic devices. The manipulation of the electron spin, on the other hand, has been proved to be more challenging because of its quantum mechanical nature. To elucidate the physics and to design applications of the electron spin, a research area named spintronics has been established, and its rapid advance has identified the essential role of the electron spin in many fundamental properties of condensed matter systems such as the spin Hall effect[2] and the quantum spin Hall effect[3]. In addition, the research on the electron spin has resulted in numerous applications such as the giant magnetoresistance structures and tunneling magnetoresistance devices[4].

Semiconductor Quantum Wires (QW) are nanoscale structures of semiconductor material whose electro-optical properties are heavily influenced by electron quantum confinement effects, due to their small structure. These structures show great promise for use in applications including sensors, quantum computing, bioelectronic and solar cells [1, 2, 3]. It is stated that, traditionally, 3D structures of QW are fabricated using high-resolution lithography. This is a very complex and expensive method making it less appealing for large scale production of QW devices. A team at the Rudjer Boskovic Institute in Croatia, in collaboration with the National Institute of Chemistry (Ljubljana) and the Slovak Academy of Sciences developed a simple method for tuning the parameters of the QW lattice unit cell by depositing self-assembling Germanium (Ge) QW in an Alumina (Al₂O₃) matrix by co-sputtering [4]. This straightforward approach involves varying the Ge DC sputtering power, in order to control the Ge concentration in the matrix, and the temperature of the substrate during the deposition.

For nearly a decade the Kurt J Lesker Company has been shipping Physical Vapor Deposition (PVD) tools into the field of perovskite solar cells around the world and continues to support world class research into this exciting technology. A key topic in the fabrication of vapor deposited perovskite photovoltaics is how much the crystal grain boundaries affect the solar cell performance (see Figure 1). Recent work, published in ACS Energy Letters, titled "Control over crystal size in vapor deposited metal-halide perovskite films' by Killian Lohmann, Jay Patel, Mathias Uller Rothmann, Chelsea Xia, Robert Oliver, Laura Herz, Henry Snaith and Michael Johnston from the University of Oxford, in the UK, has not only identified key parameters that effect the grain growth in perovskite thin films but the team has also developed a novel method to control the deposition of the organic precursor, resulting in highly efficient solar cells.

KJLC recommends that a crucible liner be filled somewhere between 2/3 and 3/4 full when beginning deposition. The melt level should not go below 30% at any time or there becomes a risk of the beam striking the crucible, causing it to break.

The Kurt J. Lesker Company continues to support the researchers who are advancing the science and technology of spintronics around the world. Co₂MnGa, a Heusler material, has been attractive to scientists as a novel magnetic conducting material on which spintronic structures like magnetic tunnel junctions can be built. Recent work, published in Applied Physics Letter titled "Perpendicular magnetic anisotropy in Co₂MnGa and its anomalous Hall Effect" by Dr. Ludbrook, Dr. Ruck and Dr. Granville from Victoria University of Wellington, New Zealand, has identified characteristics of thin film Co₂MnGa that are necessary for realizing magnetic tunnel junctions.

Selecting the correct thermal evaporation source can sometimes prove difficult. There are several factors that will need to be considered when doing so.

Dr. Zhigang Xiao, Professor of Electrical Engineering at Alabama A&M University, in collaboration with the ALD group in the Kurt J. Lesker Company recently developed the plasma-enhanced atomic layer deposition process and grow high dielectric constant (K) oxide for the application of electronic materials. They grew nanoscale hafnium dioxide (HfO₂) and zirconium dioxide (ZrO₂) thin films using remote plasma-enhanced atomic layer deposition (PE-ALD) and fabricated complementary metal-oxide semiconductor (CMOS) integrated circuits using the HfO₂ and ZrO₂ thin films as the gate oxide. Miniaturization in modern semiconductor industry requires thin film deposition to have atomic level control and the deposited film to be conformal and pinhole-free. As MOSFETs are scaled down to nanometer sizes, the tunneling currents through the gate dielectrics (the gate leakage current) has become a major concern in today’s fabrication of integrated circuits (ICs). High-K dielectric metal oxide could be a solution to the problem of the gate leakage current. The plasma-enhanced atomic layer deposition of HfO₂ and ZrO₂ thin films meets the requirement and can produce conformal and ultra-thin films with precise thickness control at the atomic layer level. The experimental results measured from the HfO₂ and ZrO₂ thin films were compared.