[en] Economic dispatch (ED) of a grid connected and renewable integrated microgrid system is considered in this paper. Two wind farms take the renewable energy sources (RES) into consideration. A parameter worst-case-transaction-cost which arises due to the stochastic availability and uncontrollable nature of wind farms is also emphasised and efforts have been taken to minimize it too. Hence the paper’s focus into split objective functions and the generation costs and the worst case transaction costs are optimised separately and also the net microgrid cost is optimized as a whole. Two different cases with highly varying transaction prices are studied. Two meta-heuristic soft computing algorithms are applied for optimization and a comparative analysis among them is studied. Numerical results are tabulated to justify the effectiveness of the novel approach.

[en] We report on high-responsivity metal-semiconductor-metal (MSM) structure based ultraviolet (UV) GaN photodetectors fabricated on various GaN nanostructures such as porous nanocolumn network (PNCN), nanowall networks (NWNs), and granular and compact thin films. Different GaN nanostructures were hetero-epitaxially grown on c-sapphire using laser molecular beam epitaxy by tuning the AlN buffer layer growth parameters. High resolution x-ray rocking curve measurements indicate that the crystalline quality of GaN critically depends on the selection of AlN buffer layer growth conditions such as type of ablation target and growth temperature. The porous GaN nanostructures revealed a nearly stress-free wurtzite structure as deduced by Raman spectroscopy measurements. Room temperature photoluminescence spectroscopy showed that the GaN films possess a near band emission (NBE) peak at ∼ 3.39 eV along with a broad yellow luminescence (YL) with maxima at 2.25 eV. For GaN PNCN and NWN structures, the NBE-to-YL emission ratio is more than an order higher compared to the GaN films. The fabricated MSM based UV-detector on GaN PNCN and NWN exhibited a high photo-responsivity of ∼27.72 and 24.8 A/W, respectively, under 2 V applied bias at room temperature. The GaN PNCN and NWN nanostructures with excellent photo-responsivity and optical quality prove to be promising candidates for the fabrication of efficient UV photodetectors due to their continuity in lateral direction, high surface area-to-volume ratio and tailored surfaces.

[en] Since the discovery of topological insulators (TIs), there are considerable interests in demonstrating metallic surface states (SS), their shielded robust nature to the backscattering and study their properties at nanoscale dimensions by fabricating nanodevices. Here we address an important scientific issue related to TI whether one can clearly demonstrate the robustness of topological surface states (TSS) to the presence of disorder that does not break any fundamental symmetry. The simple straightforward method of FIB milling was used to synthesize nanowires of Bi₂Se₃ which we believe is an interesting route to test robustness of TSS and the obtained results are new compared to many of the earlier papers on quantum transport in TI demonstrating the robustness of metallic SS to gallium (Ga) doping. In the presence of perpendicular magnetic field, we have observed the co-existence of Shubnikov–de Haas oscillations and linear magnetoresistance (LMR), which was systematically investigated for different channel lengths, indicating the Dirac dispersive surface states. The transport properties and estimated physical parameters shown here demonstrate the robustness of SS to the fabrication tools triggering flexibility to explore new exotic quantum phenomena at nanodevice level. (letter)

[en] In the last few years, research based on topological insulators (TIs) has been of great interest due to their intrinsic exotic fundamental properties and potential applications such as quantum computers or spintronics. The fabrication of TI nanodevices and the study of their transport properties has mostly focused on high quality crystalline nanowires or nanoribbons. Here, we report a robust approach to Bi₂Se₃ nanowire formation from deposited flakes using an ion beam milling method. Fabricated Bi₂Se₃ nanowire devices were employed to investigate the robustness of the topological surface state (TSS) to gallium ion doping and any deformation in the material due to the fabrication tools. We report on the quantum oscillations in magnetoresistance (MR) curves under the parallel magnetic field. The resistance versus magnetic field curves are studied and compared with Aharonov–Bohm (AB) interference effects, which further demonstrate transport through the TSS. The fabrication route and observed electronic transport properties indicate clear quantum oscillations, and these can be exploited further in studying the exotic electronic properties associated with TI-based nanodevices. (paper)

[en] Milling of 2D flakes is a simple method to fabricate nanomaterial of any desired shape and size. Inherently milling process can introduce the impurity or disorder which might show exotic quantum transport phenomenon when studied at the low temperature. Here we report temperature dependent weak antilocalization (WAL) effects in the sculpted nanowires of topological insulator in the presence of perpendicular magnetic field. The quadratic and linear magnetoconductivity (MC) curves at low temperature (>2 K) indicate the bulk contribution in the transport. A cusp feature in magnetoconductivity curves (positive magnetoresistance) at ultra low (<1 K) temperature and at magnetic field (<1 T) represent the WAL indicating the transport through surface states. The MC curves are discussed by using the 2D Hikami–Larkin–Nagaoka theory. The cross-over/interplay nature of positive and negative magnetoresistance observed in the MR curve at ultra-low temperature. Our results indicate that transport through topological surface states (TSS) in sculpted nanowires of Bi₂Te₃ can be achieved at mK range and linear MR observed at ∼2 K could be the coexistence of electron transport through TSS and contribution from the bulk band. (paper)

[en] Highlights:• Novel optical device based on Topological Insulator - Carbon Nanotubes hybrid for broadband photodetection was developed.• Efficient light absorption and electron-hole pair generation observed under illumination of visible and NIR laser light.• Excellent photodetection properties with high photoresponsivity and photoconductive gain was demonstrated by the hybrid. -- Abstract: Topological insulators represent a new electronic phase which comes from the topological character of the bulk wave functions in some special materials. These exotic phases can be attributed to the strong spin-orbit interaction and can be explained with the band theory of solids. Recent studies show that topological insulators (TIs) such as Bi₂Te₃ or Bi₂Se₃ have promising candidature for optoelectronic industry and some of these interesting properties have been already demonstrated such as strong light absorption, photocurrent sensitivity to the polarization of light, layer thickness and size dependent tuning in the band gap. Theoretically, it has been proposed that TIs based broad spectral photodetector has potential in analogy with that of a graphene based photodetector. Combining TIs with carbon-based nanomaterials provides novel and promising technique for photodetection, and can show broad spectral properties. Along this line, we have grown photodetector based on hybrid of TIs with carbon nanotubes. Efficient light absorption and electron hole pair generation has been observed under the illumination of visible (532 nm) and NIR (1064 nm) light. High photoresponsivity and photoconductive gain of 79.4 AW^-1 and 185, respectively, along with very good detector response time were observed in our device under visible laser (532 nm) illumination.

[en] Highlights: • Nanostructured Cu₂ZnSnS₄ (CZTS) thin film was grown using a sputtering method. • The optical absorbance coefficient of rln CZTS films was of the order of 10⁵/cm⁻¹. • Self-powered broadband photodetection has been reported. • The rise and decay time constants were very low. Nanostructured materials exhibit broad spectral photodetection, strong light matter interaction and exotic optoelectronic properties compared to their bulk counterpart. To overcome the limitations of silicon based photodetectors, various nanomaterials have been investigated. Here we have used industrially viable stacked layer reactive sputtering method to grow rice-like nanostructured (rln) Cu₂ZnSnS₄ (CZTS) thin films. The rln-CZTS film showed optical absorption coefficient one order of magnitude greater than the plain thin films of CZTS. Further, even under zero bias condition, broad spectral response (in visible and near infrared range) was observed. The rise and decay time constants for visible (532 nm) and near infrared (NIR) (1064 nm) light incident were 208 ms, 175 ms and 681 ms, 778 ms, respectively (for 1 mV bias). The improvement in photocurrent has been attributed to enhanced light harvesting due to the presence of nanostructures in thin film. Detectivity of 4.48 × 10⁸ Jones over a large area was observed indicating that rln-CZTS would be a potential material for other technical applications. Deposition of nanostructured CZTS using industrially viable reactive sputtering with short anneal and fabrication of self-powered broadband photodetection device with low rise and decay time constants are the novelties of this work.