Dimitrios Kaltsas

National Technical University of Athens | NTUA · Department of Physics

Growing continuous monolayer films of transition-metal dichalcogenides (TMDs) without the disruption of grain boundaries is essential to realize the full potential of these materials for future electronics and optoelectronics, but it remains a formidable challenge. It is generally believed that controlling the TMDs orientations on epitaxial substra...

Copper thiocyanate (CuSCN) is a p-type semiconductor that exhibits hole-transport and wide-band gap (∼3.9 eV) characteristics. However, the conductivity of CuSCN is not sufficiently high, which limits its potential application in optoelectronic devices. Herein, CuSCN thin films were exposed to chlorine using a dry etching system to enhance their el...

Topotactic transformations of suitable layered three-dimensional precursors are among the most robust methods to prepare two-dimensional (2D) materials based on silicon or germanium. Here we use Density Functional Theory calculations to probe the mechanisms underlying the formation of 2D-Si sheets functionalized with iodine atoms (SiI) or acetonitr...

This work introduces an alternative printing approach based on the Laser Induced Forward Transfer (LIFT) technique for the successful digital transfer of graphene, the 2D material par excellence. Using LIFT, CVD graphene pixels of 30 μm x 30 μm in size are transferred on SiO2/Si and flexible polymer substrates. The potential of upscaling this novel...

Self‐assembled monolayers (SAMs) based on Br‐2PACz ([2‐(3,6‐dibromo‐9H‐carbazol‐9‐yl)ethyl]phosphonic acid) 2PACz ([2‐(9H‐Carbazol‐9‐yl)ethyl]phosphonic acid) and MeO‐2PACz ([2‐(3,6‐dimethoxy‐9H‐carbazol‐9‐yl)ethyl]phosphonic acid) molecules were investigated as hole‐extracting interlayers in organic photovoltaics (OPVs). The highest occupied molec...

The stability of two-dimensional (2D) transition metal di-chalcogenides (TMDC) is controlled by the fact that sulfur or selenium atoms can cap the 2D layers without exposing highly reactive bonds. Here we use first-principles calculations to show that a similar structural motif can stabilize Mo- and W-based 2D materials with thio- or seleno-cyanate...

Transition metal dichalcogenides (TMDC) are currently among the most studied two-dimensional (2D) materials. Based on first-principles calculations we propose a new family of 2D materials which resemble TMDC's, but contain more complex chemical groups instead of elemental chalcogen atoms. In particular, we identify various stable 2D polymorphs of m...

Experimental studies have shown that honeycomb silicene layers can grow on various metal substrates. Here we demonstrate using first-principles calculations that hydrogenation and calcium intercalation can be employed to break bonds between a silicene overlayer and a silver surface. The end result of the former process is the creation of a silicane...

Germanane (GeH) and silicane (SiH) are the fully hydrogenated forms of germanene and silicene, the Ge- and Si-analogues of graphene. Here we use density-functional theory calculations to probe the properties of GeH and SiH sheets and their dependence on applied uni-axial compression. We find that GeH polymorphs with distinct hydrogen arrangements h...

Recent studies have examined the possibility of growing honeycomb silicene and germanene, the silicon and germanium analogues of graphene. Here we use first-principles calculations to examine the relative stability of a number of other single-layer structures that are derived from prominent surface reconstructions of group-IV semiconductors. We fin...

In the quest for the construction of silicene, the silicon analogue of graphene, recent experimental studies have identified a number of distinct ultrathin Si over-layer structures on a Ag(111) surface. Here we use first-principles calculations to probe associated atomic-scale mechanisms that can give rise to this rich behavior of Si wetting layers...