We have examined the influence of flake-substrate effects that affect one and few layers of MoS ₂ in terms of their electrical and optical properties. In the measurements, we used SiO ₂ /Si substrates with etched cavities and aluminum electrodes. Suspended areas are easily identifiable both on images depicting the topography and on the surface potential maps measured with the Kelvin probe force microscopy. Compared to the SiO ₂ /Si supported material, surface potential decrease is observable at the membrane. The surface potential value of the flakes located on the electrodes is the lowest. PL measurements prove that single MoS ₂ monolayer was obtained. Suspended regions are also correlated with maps obtained as a result of Raman spectroscopy.

We present studies focused on the evolution of the electronic band structure of the Mo_1–xW_xSe₂ alloy with the tungsten content, which was conducted by combining experimental and theoretical methods. Employed spectroscopic techniques, namely, photoreflectance, photoacoustic spectroscopy, and photoluminescence, allowed observing indirect and direct transitions at high and beyond high-symmetry points of the Brillouin zone (BZ). Two excitons (A and B) associated with the K point of the BZ were observed together with other optical transitions (C and D) related to band nesting. Moreover, we have also identified the indirect transition for the studied crystals. Obtained energies for all transitions were tracked with a tungsten content and compared with results of calculations performed within density functional theory. Furthermore, based on the mentioned comparison, optical transitions were assigned to specific regions of the BZ. Finally, we have obtained bowing parameters for experimentally observed features, for, i.e., thin-film samples: b(A) = 0.13 ± 0.03 eV, b(B) = 0.14 ± 0.03 eV, b(C) = 0.044 ± 0.008 eV, and b(D) = 0.010 ± 0.003 eV.

To obtain molecularly thin flakes via mechanical exfoliation from a bulk layered crystal, the process should be repeated multiple times, but the mathematical principle behind this phenomenon remains unknown. In this paper, we show how the thickness of the MoS₂ flake changes with subsequent cleavages of the adhesive tape, with the tests carried out on two widely used dicing tapes and Scotch removable tape. In the beginning, we assumed that with each subsequent tear of the tape, the thickness of the material decreases by half. We discovered that the exfoliated crystal thickness decreases with geometric progress and proposed a formula depicting that phenomenon. In addition, the exfoliated flakes are observed to crumble during the process and the fragmentation factor is discussed as well. Our observations will allow for more efficient estimation of the number of steps required to produce a sample of the desired thickness, relevant for tuning electronic transport properties and optical activity of two-dimensional materials.

Boron doped diamond (BDD) has great potential in electrical, and electrochemical sensing applications. The growth parameters, substrates, and synthesis method play a vital role in the preparation of semiconducting BDD to metallic BDD. Doping of other elements along with boron (B) into diamond demonstrated improved efficacy of B doping and exceptional properties. In the present study, B and nitrogen (N) co-doped diamond has been synthesized on single crystalline diamond (SCD) IIa and SCD Ib substrates in a microwave plasma-assisted chemical vapor deposition process. The B/N co-doping into CVD diamond has been conducted at constant N flow of N/C ∼ 0.02 with three different B/C doping concentrations of B/C ∼ 2500 ppm, 5000 ppm, 7500 ppm. Atomic force microscopy topography depicted the flat and smooth surface with low surface roughness for low B doping, whereas surface features like hillock structures and un-epitaxial diamond crystals with high surface roughness were observed for high B doping concentrations. KPFM measurements revealed that the work function (4.74–4.94 eV) has not varied significantly for CVD diamond synthesized with different B/C concentrations. Raman spectroscopy measurements described the growth of high-quality diamond and photoluminescence studies revealed the formation of high-density nitrogen-vacancy centers in CVD diamond layers. X-ray photoelectron spectroscopy results confirmed the successful B doping and the increase in N doping with B doping concentration. The room temperature electrical resistance measurements of CVD diamond layers (B/C ∼ 7500 ppm) have shown the low resistance value ∼9.29 Ω for CVD diamond/SCD IIa, and the resistance value ∼16.55 Ω for CVD diamond/SCD Ib samples.