Alexandra Davydova

Uppsala University | UU · Department of Engineering Sciences

Complex compound semiconductors, such as the emerging solar cell material Cu2ZnSn(S,Se)4 (CZTS), present major experimental challenges in terms of understanding and controlling growth processes and defect formation. This study aims to shed light upon the complicated interplay of the synthesis conditions and CZTS thin film properties. Composition-sp...

Tandem solar cells based on hybrid organic-inorganic metal halide perovskites have reached efficiencies up to 28%, but major concerns for long-term stability and the presence of Pb have raised interest in searching for fully earth-abundant, intrinsic chemically stable, and non-toxic alternatives. With a direct band gap around 1.8 eV and stability i...

Cu2ZnSnS4 (CZTS) is hoped to be a future, earth-abundant absorber material for thin film solar cells, but performance remains below the level needed for commercialization. In this work, the size of the single phase region of CZTS obtained from thin film synthesis methods is explored, to determine the scope available for defect engineering and there...

Thio-olivines such as (Fe,Mn)2(Si,Ge)S4 have been proposed as candidate earth-abundant materials for single and multi-junction solar cells. In this work we present the first investigation of Mn2SiS4thin films prepared by reactive magnetron sputtering deposition, using a composition grading approach. Precursor instability in ambient conditions is ob...

Cu-Zn disorder in Cu2ZnSnS4 (CZTS) may be responsible for the large open circuit voltage deficit in CZTS based solar cells. In this study, it was investigated how composition-dependent defect complexes influence the order-disorder transition. A combinatorial CZTS thin film sample was produced with a cation composition gradient across the sample are...

We report the manufacturing of thin zinc oxide films by reactive magnetron sputtering at room temperature, and examine their structural and optical properties. We show that the partial oxygen pressure in DC mode can have dramatic effect on absorption and refractive index (RI) of the films in a broad spectral range. In particular, the change of the...

H⁺ ion-induced damage of multilayergraphene (MLG) is investigated using Molecular Dynamics simulations as H2 plasmas could provide a possible route to pattern graphene. Low-energy (5–25 eV) H⁺ cumulative bombardment of ABA-stacked MLG samples shows an increase of the hydrogenation rate with the ion dose and ion energy. At 5 eV, the H coverage grows...

Graphene outstanding properties created a huge interest in the condensed matter community and unprecedented fundings at the international scale in the hope of application developments. Recently, there have been several reports of incomplete removal of the polymer resists used to transfer as-grown graphene from one substrate to another, resulting in...

To assist the development of plasma processes to pattern graphene in a controlled way, interactions between hydrogen plasma species (H, H+, H2+) and various types of graphene surfaces (monolayer, nanoribbons, multilayer) are investigated using atomic-scale simulations. It is shown that only “hot” H particles (i.e., with a kinetic energy greater tha...

Graphene is the first engineering electronic material, which is purely two-dimensional: it consists of two exposed sp2-hybridized carbon surfaces and has no bulk. Therefore, surface effects such as contamination by adsorbed polymer residues have a critical influence on its electrical properties and can drastically hamper its widespread use in devic...

Lateral etching mechanisms of graphene nanoribbons (GNRs) with zigzag (ZZ) edges in downstream H2 plasmas are investigated using molecular dynamics simulations. A new etching mechanism is found, which occurs in three consecutive phases and requires a continuous exposure of GNRs to H atoms and high substrate temperatures (~800 K). Full hydrogenation...

Elementary interactions between H atoms and monolayer graphene are investigated using classical molecular dynamics (CMD) and density functional theory (DFT). C-H interatomic potential curves and associated energy barriers are reported depending on the H impact position (top, bridge, hollow, vacancy, or edge sites of graphene nanoribbons). Chemisorp...

Development of graphene-based technologies relies on the capability to grow and integrate this new material into sophisticated devices but the nm-scale control of graphene processing challenges current processing technology. Plasma-graphene interactions must be carefully controlled to avoid damage to the active layers of graphene-based nanoelectron...