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We report the results of a study of the sulphurization time effects on Cu2ZnSnS4 absorbers and thin film solar cells prepared from dc-sputtered stacked metallic precursors. Three different time intervals, 10 min, 30 min and 60 min, at maximum sulphurization temperature were considered. The effects of this parameter' change were studied both on the absorber layer properties and on the final solar cell performance. The composition, structure, morphology and thicknesses of the CZTS layers were analysed. The electrical characterization of the absorber layer was carried out by measuring the transversal electrical resistance of the samples as a function of temperature. This study shows an increase of the conductivity activation energy from 10 meV to 54 meV for increasing sulphurization time from 10 min to 60 min. The solar cells were built with the following structure: SLG/Mo/CZTS/CdS/i-ZnO/ZnO:Al/Ni:Al grid. Several ac response equivalent circuit models were tested to fit impedance measurements. The best results were used to extract the device series and shunt resistances and capacitances. Absorber layer's electronic properties were also determined using the Mott-Schottky method. The results show a decrease of the average acceptor doping density and built-in voltage, from 2.0×10 17 cm −3 to 6.5×10 15 cm −3 and from 0.71 V to 0.51 V, respectively, with increasing sulphurization time. This results also show an increase of the depletion region width from approximately 90 nm to 250 nm.

Diamond is known as a promising electrode material in the fields of cell stimulation, energy storage (e.g., supercapacitors), (bio)sensing, catalysis, etc. However, engineering its surface and electrochemical properties often requires costly and complex procedures with addition of foreign material (e.g., carbon nanotube or polymer) scaffolds or cleanroom processing. In this work, we demonstrate a novel approach using laser-induced periodic surface structuring (LIPSS) as a scalable, versatile, and cost-effective technique to nanostructure the surface and tune the electrochemical properties of boron-doped diamond (BDD). We study the effect of LIPSS on heavily doped BDD and investigate its application as electrodes for cell stimulation and energy storage. We show that quasi-periodic ripple structures formed on diamond electrodes laser-textured with a laser accumulated fluence of 0.325 kJ/cm2 (800 nm wavelength) displayed a much higher double-layer capacitance of 660 μF/cm2 than the as-grown BDD (20 μF/cm2) and that an increased charge-storage capacity of 1.6 mC/cm2 (>6-fold increase after laser texturing) and a low impedance of 2.74 Ω cm2 turn out to be appreciable properties for cell stimulation. Additional morphological and structural characterization revealed that ripple formation on heavily boron-doped diamond (2.8 atom % [B]) occurs at much lower accumulated fluences than the 2 kJ/cm2 typically reported for lower doping levels and that the process involves stronger graphitization of the BDD surface. Finally, we show that the exposed interface between sp2 and sp3 carbon layers (i.e. the laser-ablated diamond surface) revealed faster kinetics than the untreated BDD in both ferrocyanide and RuHex mediators, which can be used for electrochemical (bio)sensing. Overall, our work demonstrates that LIPSS is a powerful single-step tool for the fabrication of surface-engineered diamond electrodes with tunable material, electrochemical, and charge-storage properties.

switches for wireless communication systems, as it promises high operating frequency in the GHz range, as well as narrow bandwidth (high Q-factor) and low phase noise. [1][2][3] This is thanks to diamond's excellent material properties, such as high Young's modulus (up to ≈10 6 N mm −2 ), high acoustic velocity (≈1.8 × 10 4 m s −1 ), [3] low thermoelastic damping, high thermal conductivity (>2000 W m −1 K −1 ), and low thermal expansion coefficient (≈10 −6 K −1 at 300 K). [4] The feasibility of using NCD for high-performance MEMS resonators has already been demonstrated in a range of devices, including cantilever beams, [5,6] tuning forks, [7] rings, [8] disks, [9][10][11] and spheres. [12] In particular, NCD MEMS structures that resonate with whispering gallery modes (WGM), such as disks and spheres, have shown much lower anchor losses and higher (f 0 × Q) figure of merit. [3,11] However, despite the recent progress, adding diamond structures into integrated circuits for a complete functional device remains a challenge. The current limitations relate to the difficulty in combining NCD with other microfabricated structures, mostly due to nanodiamond seeding requirements, but also due to the harsh environment during chemical vapor deposition (CVD) of the NCD film, as well as mechanical issues caused by intrinsic stress in the film. [13] Nanodiamond seeding in particular suffers from the process not being selective, i.e., instead of diamond being deposited and grown only where it is required on the device, most established methods consist of dispersing nanodiamond over a large substrate by, e.g., dip-coating, dropcasting, or spin-seeding, prior to film growth by CVD. [14] The grown NCD film needs then to be patterned by traditional photo-/e-beam lithography and lift-off techniques, which add substantial complexity and cost of fabrication. As a solution to circumvent low seeding density and plasma uniformity issues during growth of the NCD layer, Lebedev et al. proposed waferto-wafer bonding of pregrown NCD films onto another wafer to fabricate NCD disk resonators with high Q-factors (i.e., Q > 10 3 ). [9] This technique however did not remove the need to pattern the diamond after it was bonded onto the wafer. Possas et al. demonstrated the fabrication of NCD cantilever beams by patterning the nanodiamond seeding layer by means of sacrificial metal layer and etching, [15] but still top-down patterning by lithography was required. Akgul et al. reported Q-factors of the order of 7 × 10 4 for on-chip NCD disk resonators which required up to five masking/etching steps. [11] Yang et al., on the Diamond is a highly desirable material for state-of-the-art micro-electromechanical (MEMS) devices, radio-frequency filters and mass sensors, due to its extreme properties and robustness. However, the fabrication/integra tion of diamond structures into Si-based components remain costly and complex. In this work, a lithography-free, low-cost method is introduced to fabricate diamond-based micro-resonators: a modified home/office d...