Fabrication of practical devices based on the transient metal dichalcogenides (TMDs) can be successively extended to various areas of the applications if the large area growth technology can be intentionally controlled and the characteristics of the layers can be easily predicted. In present work we presented the principles of the technology control based on the single key variable that can be directly related to the sequence of the technological processes. The atomically thin MoS2 layers were used as a model material and the layers were obtained by the CVD synthesis of the molybdenum precursor. Our thorough study demonstrated that the method allowed to deliberately choose the number of the MoS2 two-dimensional (2D)-layers between 1 and 10 by simply choosing the precursor deposition time. The optical properties of the layers were characterised by the optical transitions that corresponded to the known band structure of the MoS2 layers. Fused calibration diagram was proposed as the practical tool for the technology control and it was proved to be highly successive in relating the 2D-properties of the films with the initial stage of the fabrication technology. The method can be adapted to the wafer size TMDs growth on the diverse substrates.

Chemical vapour deposition (CVD) graphene is commonly recognized as promising 2D material for development of electronic devices. However, the long-term drift of electrical parameters still requires deeper understanding before the technological means can be selected for an individual type of the devices. In this work, the changes in the electrical resistance were investigated over long time in the planar samples based on the CVD graphene with Au and Ni contacts. The samples were arranged as arrays of the resistors on a silicon substrate covered with a 250 nm layer of thermally grown silicon dioxide. The annealing in pure argon gas flow at 573 K was used to return the electrical properties of samples to the initial state. The effects of drift and annealing were compared for the three parts of structures, namely the electrical contact, the graphene sheet and the edge of the metal film with a hanging graphene sheet. For these parts, the resistance changes were related to the strain and doping of supported and hanged parts of the graphene sheet. Raman spectroscopy and Kelvin force probe microscopy were used to characterize charge doping, strain and work function in the graphene. The drift was explained in terms of the most prominent changes in the doping, strain and work function detected within the edge zone of the contact. It was proved that the annealing significantly changed the p-type doping and work function in the graphene layer in this edge zone. The properties were almost independent of test conditions in the SiO2 supported graphene. The changes in the contact parameters produced by drift mechanisms were proved being reversible under proper annealing conditions.

Here we present a study of the nickel-assisted etching applied to form uniform black silicon layers on crystalline silicon substrates. We related the parameters used for technological process control (etchant, nickel thickness) to parameters of the obtained surface and explain the correlation using the etching model responsible for etching of the silicon covered by a thin nickel film. The increase in the thickness of the metal catalyst did not suppress the etching completely but allowed one to tune the roughness of the silicon surface. The rate of the electrochemical etching was additionally changed by adaptation of the proportion of components in the complex etchant. Depending on the intentionally selected conditions, the duration of the optimized process was from 3 to 10 min. The lowest optical reflection commonly accepted as the black silicon surface was obtained for the mixture with a low amount of the active etchant component. It was demonstrated that the method is acceptable to improve the characteristics of a photovoltaic cell.

The development of technologies of hybrid structures with combined three-dimensional (3D) and two-dimensional (2D) materials is being recognised as a highly attractive opportunity to create new optoelectronic devices with unique properties originating from the atomic thin structures. In the present study, a novel approach in the direct synthesis of MoS2 2D-layers on p-Si was proved to be acceptable for fabricating a photovoltaic effect–driven photodetector based on a hybrid 2D/3D heterojunction that included an atomically thin n-MoS2 film and crystalline p-Si substrate. It was demonstrated experimentally that the heterojunction with the top and bottom contacts was highly sensitive to illumination between 650 and 1200 nm. The experimental study proved that the response to light was originated by the photovoltaic effect in the sample devices without an external power supply. The maximum sensitivity of the 2D/3D heterostructures to the optical power of the illumination was up to 210 V W−1 and was practically independent of the wavelength. The analysis of experimental I–V, C-V characteristics, Raman spectra and AFM surface images allowed us to construct a flat band model of the hybrid 2D/3D n-p-heterojunction that explained the electrical properties of the n-MoS2/p-Si photodetectors. The photovoltaic effect-driven light detectors offer highly promising possibilities in the development of autonomous photonic systems.

Laser diodes with parabolic and rectangular AlGa(As,Bi)/AlGaAs QWs were grown by MBE on n-GaAs(001). Operating wavelength was controlled by QW width and material composition. Laser bars processed by UV lithography were characterized by electroluminescence and I-V measurements.

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