Nanostructured Semiconductor Materials Research Articles

Experimental and Theoretical Investigation of Zr‐Doped CuO/Si Solar Cell

Copper oxide (CuO) is a nanostructured semiconductor material with the potential for solar energy conversion and can be suitable for solar cells when used as a thin film. Herein, nondoped and doped (doping ratios of 1%, 2%, and 3% zirconium [Zr]) CuO thin films on silicon (Si) with the spin‐coating technique are developed. Optical and topological characterizations of CuO thin films are examined by ultraviolet‐visible and X‐ray diffraction. The electrical properties of nondoped and Zr‐doped CuO/Si heterojunctions are investigated with experimental current–voltage measurements in the dark and under illuminated conditions. The electrical behavior of nondoped and Zr‐doped CuO/Si heterojunctions is obtained using the experimental J–V technique and computational Cheung–Cheung and Norde methods. A simulation based on nondoped and Zr‐doped CuO/n‐Si heterojunction solar cells using SCAPS‐1D is completed. Photovoltaic (PV) parameters of experimentally produced and theoretically calculated CuO and Zr‐doped CuO/Si heterojunction solar cells are compared. Accordingly, PV parameters of 1% Zr‐doped CuO/Si solar cells show the highest power conversion efficiency calculated as a function of interfacial defect density and hole carrier concentration.

Non-thermal regimes of laser annealing of semiconductor nanostructures: crystallization without melting

As-prepared nanostructured semiconductor materials are usually found in an amorphous form, which needs to be converted into a crystalline one for improving electronic properties and achieving enhanced application functionalities. The most utilized method is thermal annealing in a furnace, which however is time- and energy-consuming and not applicable for low-temperature melting substrates. An alternative is laser annealing, which can be carried out in a relatively short time and, additionally, offers the possibility of annealing localized areas. However, laser-annealed nanostructures are often distorted by melting, while preserving the as-prepared morphology is essential for practical applications. In this work, we analyze conditions of non-thermal ultrafast laser annealing of two kinds of nanostructures: anodic TiO2 nanotube layers and Ge/Si multilayer stacks. For both cases, regimes of crystallization have been found, which yield in preserving the initial nanomaterial morphologies without any melting signs. On these examples, ultrafast non-thermal mechanisms of structural material transformation are discussed, which can provide new opportunities for conversion of amorphous semiconductor nanomaterials into a desired crystalline form that is of high demand for existing and emerging technologies.

CO2 electro/photocatalytic reduction using nanostructured ZnO and silicon-based materials: A short review

Reducing CO2 net emissions is one of the most pressing goals in tackling the current global warming emergency. Therefore, the development of carbon recycling strategies has resulted in the application of heterogeneous catalysts toward the electro/photocatalysis reduction of CO2 into hydrocarbons with potential reusability. Their morphology is among the properties that affect the performance and selectivity of catalysts towards this reaction. Nanostructuring methods offer popular strategies for catalytic applications since they allow an increase in the area/volume ratio and versatile control over surface physicochemical properties. In this review, we summarize studies that report the use of versatile synthesis techniques for obtaining nanostructured metallic and semiconductor materials with application in the electro/photocatalytic reduction of CO2. Enhancing mechanisms to the catalytic CO2 reduction yield, such as improved charge carrier separation efficiency, defect engineering, active site concentration, and localized plasmonic behavior, are described in conjunction with the control over the morphologies of the nanostructured platforms. Special attention is given to ZnO and silicon-based matrices as candidates for developing abundant and non-toxic catalytic materials. Therefore, this work represents a guide to the efforts made to design electro/photocatalytic systems that can contribute significantly to this field.

Surface and Constriction Engineering of Nanoparticle Based Structures Towards Ultra-Low Thermal Conductivity as Prospective Thermoelectric Materials

ABSTRACT The superior thermal insulating properties of nanostructured semiconductor materials over their bulk counterparts, make them promising candidates for Thermo-Electric (TE) applications. In this study, the superior thermal insulating properties of a new class of one-dimensional nanostructures made by sintering linearly placed nanoparticles, called Nano Particle Chains (NPC) are analyzed for a variety of surface and constriction modifications. The NPC structure which has been shown to be capable of achieving a one-order reduction in thermal conductivity over comparably sized nanowires is revealed to house a new phonon suppression mechanism in addition to commonly discussed phonon boundary scattering and quantum confinement effects. In the current work, this quantum confinement based thermal conductivity reduction mechanism is revealed to be a variation in the phonon Density of States (DoS) along the longitudinal/transport direction of the structure due to the presence of the nanoscale constrictions. Subsequently, the phonons are forced to change the distribution of modes while traveling across the structure, thus resulting in lower thermal conductivity. Additionally, the effects of common phonon suppression techniques such as superlattice, shell alloy, and surface atom removal, used in semiconductor nanostructures are also evaluated on NPC configurations to fully determine the phonon transport characteristics within different classes of the material.

GaN/ZnO hybrid nanostructures for improved photocatalytic performance: One-step synthesis.

Nanostructured semiconductor materials are considered potential candidates for the degradation of textile wastewater via the photocatalytic process. This study aims to produce hexagonal gallium nitride (GaN) nanoplates and zinc oxide (ZnO) nanoparticles in a deionized water environment utilizing a one-step arc discharge process. Detailed characterization of samples has been completed via scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV visible spectroscopy methods. The hybrid nanostructure morphologies consist of nanoplates and nanorods of different sizes. The photoperformance of GaN/ZnO hybrid nanostructures was assessed via the malachite green (MG) dye degradation under UV exposure. Under UV exposure, the degradation yield reached 98% in 60 min. Compared to individual ZnO and GaN nanoparticles, the photocatalytic reaction rate of the GaN/ZnO photocatalyst is 2.2 and 3.6 times faster, respectively. Besides, the GaN/ZnO hybrid nanostructures show excellent photocatalytic stability. The energy consumption of the photocatalytic degradation in the presence of GaN/ZnO hybrid nanostructures was 1.688 kWhL-1. These results demonstrate that the GaN/ZnO hybrid nanostructures with improved photocatalytic activity are a reasonable option for the decomposition of textile wastewater under UV light exposure.

Review on Electrochemical Sensing of Triclosan using Nanostructured Semiconductor Materials

AbstractTriclosan (TCS) is an antifungal and antimicrobic component used in various cosmetic, healthcare, and personal care products; therefore, many people are exposed to this compound. Literature and related studies have shown inflammatory skin conditions and endocrine disruption after exposure to TCS. Low concentrations of TCS released into environmental wastewater and soil eventually increase the toxicity. Hence, the detection and sensing of TCS is an important process. Nanostructured semiconductor materials are widely used for the selective and sensitive sensing of TCS because of their high accuracy, wide linear range, and high conductivity. This Review describes the progress made in the use of nanostructured particles such as metal oxides and metal oxide nanocomposite, multiwalled carbon nanotubes (MWCNTs), carbon nanodots (CNDs), graphene, molecular imprinted polymers (MIPs), organic polymers, polymer nanocomposite, quantum dots (QDs), gold nanoparticles, silver nanoparticles, and other nanoparticles as electrode active materials for the electrochemical sensing of TCS in environmental samples.

Lattice Strain and Defects Analysis in Nanostructured Semiconductor Materials and Devices by High‐Resolution X‐Ray Diffraction: Theoretical and Practical Aspects (Small Methods 2/2022)

HR-XRD Methods In article number 2100932, Neels and co-workers reviewed important theoretical and practical aspects of HR-XRD methods. In particular, they focused on nanowires, epitaxial layers, and complex sensor systems. Device fabrication processes affect the crystal lattice coherence, modify lattice strain and defects state, thus impacting on reliability and performance of devices in applications.

Nanostructured heterogeneous photocatalyst materials for green synthesis of valuable chemicals

The photocatalytic process employing nanostructured semiconductor materials has attracted great attention in energy production, CO2 reduction, and water/air purification for decades. Recently, applying heterogeneous photocatalyst for the synthesis of valuable chemicals is gradually emerging and considered as a promising process for the conversion of cheap resources (i.e., biomass derivatives, polyols, and aromatic hydrocarbons). Compared with traditional thermal catalytic approaches, the photocatalytic process provides a mild reaction condition and flexible platform (photocatalyst) that allows precise tweaking of reaction intermediates and reaction pathways, thus resulting in fine control of the selective synthesis of specialized chemicals that are challenging for thermal catalysis. In this review, we summarize recent achievements in photocatalytic synthesis of various industrial important chemicals via photo-oxidative and photo-reductive processes. The selective oxidation of alcohols and aromatics, epoxidation of alkenes, hydrogenation of gaseous molecules and hydrocarbons, and coupling reactions by means of various photocatalysts including metal oxides, supported plasmonic metal nanostructures, conjugated organic polymers, anchored homogeneous catalysts, and dye-sensitized heterostructures are discussed from a material perspective. In addition, fundamental understandings of reaction mechanisms and rational design of nanostructured photocatalysts for enhancing efficiency, selectivity, and stability are discussed in detail.

Lattice Strain and Defects Analysis in Nanostructured Semiconductor Materials and Devices by High-Resolution X-Ray Diffraction: Theoretical and Practical Aspects.

The reliability of semiconductor materials with electrical and optical properties are connected to their structures. The elastic strain field and tilt analysis of the crystal lattice, detectable by the variation in position and shape of the diffraction peaks, is used to quantify defects and investigate their mobility. The exploitation of high-resolution X-ray diffraction-based methods for the evaluation of structural defects in semiconductor materials and devices is reviewed. An efficient and non-destructive characterization is possible for structural parameters such as, lattice strain and tilt, layer composition and thickness, lattice mismatch, and dislocation density. The description of specific experimental diffraction geometries and scanning methods is provided. Today's X-ray diffraction based methods are evaluated and compared, also with respect to their applicability limits. The goal is to understand the close relationship between lattice strain and structural defects. For different material systems, the appropriate analytical methods are highlighted.

A novel and highly efficient Ag and GO co-synthesized ZnO nano photocatalyst for methylene blue dye degradation under UV irradiation

Heterogeneous photocatalysis is an effective and promising treatment technology for the removal of organic dye compounds in textile wastewater. Hybrid nanostructured semiconductor materials have been extensively applied and received greater attention in the last few decades. In this study, nano structured zinc oxide (ZnO) was doped by silver (Ag) and graphene oxide (GO) nanoparticles to synthesize Ag/GO/ZnO using the sol–gel technique followed by the heat treatment method. The hexagonal wurtzite structure of ZnO as observed by SEM was changed to lump/flake shape after doping with Ag and GO onto the ZnO crystal surface. FTIR confirms the stretching vibration of broad O–H groups with adsorbed H2O molecules. The broad absorption edge of Ag/GO/ZnO nanocomposite shifted to the visible-light region with the reduced band gap energy of 3.22 eV as compared to 3.34 for ZnO. The photocatalytic degradation of methylene blue (MB) dye (15 mgL−1) under 100 W UV irradiation was84.67%, 88.13%, and 97.53%, for ZnO, Ag/ZnO, and Ag/GO/ZnO nanocomposites, respectively, at the same dose of photocatalyst (0.300 g) and pH 11.0for3 h UV irradiation. The best fitted kinetic of photocatalytic studies were showed a pseudo-first-order reaction model and the respective rate constants were found to be 0.0129 min−1, 0.0149 min−1, and 0.5198 min−1, for ZnO, Ag/ZnO, and Ag/GO/ZnO nanocomposites, respectively. The enriched photodegradation activity of Ag/GO/ZnO nanocomposite indicates the potential of the nanocomposite for the treatment of organic pollutants from the textile wastewater.

Evaluation of bioactivities of zinc oxide, cadmium sulfide and cadmium sulfide loaded zinc oxide nanostructured materials prepared by nanosecond pulsed laser.

The present study reports the preparation of cadmium sulfide (CdS) loaded zinc oxide (ZnO) nanostructured semiconductor material and its anti-bioactivity studies against cancerous and fungus cells. For composite preparation, two different mass ratios of CdS (10 and 20%) were loaded on ZnO (10%CdS/ZnO, 20%CdS/ZnO) using a 532nm pulsed laser ablation in water media. The structural and morphological analyses confirmed the successful loading of nanoscaled CdS on the surface of ZnO particles, ZnO particles were largely spherical with average size ~50nm, while CdS about 12nm in size. The elemental and electron diffraction analyses reveal that the prepared composite, CdS/ZnO contained both CdS and ZnO, thus reaffirming the production of CdS loaded ZnO. The microscopic examination and MTT assay showed the significant impact of ZnO, CdS, and CdS loaded ZnO on human colorectal carcinoma cells (HCT-116 cells). Our results show that the prepared ZnO had better anticancer activities than individual CdS, and CdS loaded ZnO against cancerous cells. For antifungal efficacy, as-prepared nanomaterials were investigated against Candida albicans by examining minimum inhibitory/fungicidal concentration (MIC/MFC) and morphogenesis. The lowest MIC (0.5mg/mL), and MFC values (1mg/mL) were found for 10 and 20%CdS/ZnO. Furthermore, the morphological analyses reveal the severe damage of the cell membrane upon exposure of Candida strains to nanomaterials. The present study suggests that ZnO, CdS, and CdS loaded ZnO nanostructured materials possess potential anti-cancer and anti-fungal activities.

Modeling of Solution Growth of ZnO Hexagonal Nanorod Arrays in Batch Reactors

Low temperature solution growth is an attractive method for the preparation of nanostructured semiconductor materials with a wide range of applications from optoelectronics to chemical sensing. Des...

Biosynthesis of bismuth selenide nanoparticles using chalcogen-metabolizing bacteria.

Cost and energy reductions in the production process of bismuth chalcogenide (BC) semiconductor materials are essential to make thermoelectric generators comprised of BCs profitable and CO2 neutral over their life cycle. In this study, as an eco-friendly production method, bismuth selenide (Bi2Se3) nanoparticles were synthesized using the following five strains of chalcogen-metabolizing bacteria: Pseudomonas stutzeri NT-I, Pseudomonas sp. RB, Stenotrophomonas maltophilia TI-1, Ochrobactrum anthropi TI-2, and O. anthropi TI-3 under aerobic conditions. All strains actively volatilized selenium (Se) by reducing selenite, possibly to organoselenides. In the growth media containing bismuth (Bi) and Se, all strains removed Bi and Se concomitantly and synthesized nanoparticles containing Bi and Se as their main components. Particles synthesized by strain NT-I had a theoretical elemental composition of Bi2Se3, whereas those synthesized by other strains contained a small amount of sulfur in addition to Bi and Se, making strain NT-I the best Bi2Se3 synthesizer among the strains used in this study. The particle sizes were 50-100 nm in diameter, which is sufficiently small for nanostructured semiconductor materials that exhibit quantum size effect. Successful synthesis of Bi2Se3 nanoparticles could be attributed to the high Se-volatilizing activities of the bacterial strains. Selenol-containing compounds as intermediates of Se-volatilizing metabolic pathways, such as methane selenol and selenocysteine, may play an important role in biosynthesis of Bi2Se3.

Self-limiting Sb monolayer as a diffusion source for Ge doping

A new method for the creation of high-quality, fully electrically active junctions to be applied in nanostructured semiconductor materials is explored in this work. The method consists in a gas phase antimony deposition on Ge, which gives rise to an antimony self-limiting behavior to form a monolayer (ML) on the Ge (100) surface. The ML formation is characterized by a wide thermal process window in terms of time and temperature. Synchrotron radiation Angle Resolved X-ray Photoelectron Spectroscopy shows that the ML structure consists in oxidized Sb grown over a very thin layer of Ge oxide, and a small amount of metallic Sb is embedded beneath the Ge surface during the deposition process. Interestingly, during the ML formation process native Ge oxide is reduced without the need of strong acid pre-treatments. By performing further thermal annealing in equilibrium conditions, Sb diffusion can be faithfully described by a well assessed diffusion model. Finally, processing the Sb monolayer with Pulsed Laser Melting technique, which is a strongly out-equilibrium diffusion process, allows to exploit the entire Sb ML as a dopant source, thus achieving junctions with a very high dopant concentration (1.2 × 1020 cm−3 Sb surface concentration) and a 100% Sb electrical activation.

Dynamic Photoelectrochemical Device with Open-Circuit Potential Insensitive to Thermodynamic Voltage Loss.

The open-circuit potential ( Voc) represents the maximum thermodynamic potential in a device, and achieving a high Voc is crucial for self-biased photoelectrochemical (PEC) devices that use only solar energy to produce chemical energy. In general, Voc is limited by the photovoltage ( Vph), which is a potential difference generated by light-induced thermodynamic processes at semiconductor photoelectrodes, such as the generation and recombination of charge carriers. Therefore, low light intensity and nanostructured semiconductor materials degrade Vph (and Voc) by inefficient carrier generation and by enhancing recombination loss, respectively. Here, we report that Voc in dynamic PEC devices employing a porous NiO x/Si photocathode is insensitive to thermodynamic losses, which was clarified by varying the carrier generation and recombination rates. The Voc values were observed to be unchanged even under a low light intensity of 0.1 sun, as well as for different morphologies such as nanostructured and polycrystalline Si. These findings shed light on the potential merit of dynamically operated PEC systems.

Novel nanostructures of bromoaluminum phthalocyanine grown by physical vapor phase transport

The growth of new nanostructured organic semiconductor materials such as metal phthalocyanines instead of polycrystalline thin films can provide the basis for the development of various revolutionary nanodevices. In this study, we report the growth of new bromo aluminum phthalocyanine (BrAlPc) nanostructures on glass substrates, namely nanorods, nanothistles, and nanocorals, by physical vapor phase transport technique. Their Surface morphology have been investigated using field emission scanning electron microscopy, suggesting the shape and the size of nanostructures is source-substrate distance dependent. Only by varying the source-substrate distance, the perpendicular, and parallel nanorods and evenly distributed nanorods without particular orientation, were observed in the surface. All the nanostructures show two absorption bands in the visible range, namely the Q-band. In addition, analyzing the absorption spectra of the grown nanostructures reveals that the BrAlPc nanothistles is in β-phase while the other nanostructures is mainly in α-phase. Because of the variety of morphologies and the ability to achieve high surface-to-volume ratios, the BrAlPc nanostructures might be of practical value in the opto-electronic devices.

Hydrogenation and Structuration of TiO2 Nanorod Photoanodes: Doping Level and the Effect of Illumination in Trap-States Filling

Both electronic properties and light absorption are key features in materials engineering to achieve efficient photoelectrodes for water splitting. Adjusting the potential drop inside the nanostructured semiconductor material through modification of the electronic properties is mandatory to drive efficiently the photogenerated charges. In this work, a hydrogen reduction treatment on titanium dioxide rutile nanorod based photoanodes has been performed in order to adjust the donor density to maximize electron–hole separation. Also, incident photon-to-current efficiency (IPCE) measurements and the effect of a light bias have been elucidated, finding relevant differences in low illumination conditions due to nonfilled trap states. A physical model is proposed to show the role of the donor density on the overall performance of the photoanodes under study. The obtained productivity was enhanced by structuring the conductive glass substrates where TiO2 nanorods were grown, resulting in a 20% increase of the phot...

Solution, Solid-State Two Step Synthesis and Optical Properties of ZnO and SnO2 Nanoparticles and Their Nanocomposites with SiO2

Nanostructure luminescent ZnO and SnO2 materials are prepared by a two-step solid-state method based on the solution preparation of the macromolecular precursors ZnCl2·Chitosan and SnCl2·Chitosan having different ratios (1:1, 1:5 and 1:10), their pyrolysis under air at 800 °C. The pyrolytic ZnO and SnO2 nanomaterials show a dependence of the particle size, morphology and luminescent properties with the ratio [metal/polymer] in the MCl2·Chitosan precursors. Thus, ZnO semiconductor materials exhibit luminescence spectra with several emission at 440 nm corresponds to a radiative transition of an electron from the shallow donor level of oxygen vacancies, and the zinc interstitial, to the valence band. On the other hand, the photoluminescence spectrum of the nanostructured SnO2 shows an intense blue luminescence at a wavelength of 420 nm which may be attributed to oxygen-related defects that have been introduced during the growth process of the nanoparticles. Additionally, whereas SnO2 was successfully incorporated into SiO2 structure (SnO2//SiO2) by pyrolysis of solid-state mixtures of the precursors SnCl2·Chitosan in the presence of SiO2, the same reaction carried out with ZnCl2·Chitosan precursors led to a mixture of Zn2SiO4 and SiO2. Thus, this new methodology yields nanostructured semiconductor materials, ZnO and SnO2, suitable for optoelectronic and sensor solid-state devices.

Photoelectrochemical Water Oxidation by GaAs Nanowire Arrays Protected with Atomic Layer Deposited NiO x Electrocatalysts

Photoelectrochemical (PEC) hydrogen production makes possible the direct conversion of solar energy into chemical fuel. In this work, PEC photoanodes consisting of GaAs nanowire (NW) arrays were fabricated, characterized, and then demonstrated for the oxygen evolution reaction (OER). Uniform and periodic GaAs nanowire arrays were grown on a heavily n-doped GaAs substrates by metal–organic chemical vapor deposition selective area growth. The nanowire arrays were characterized using cyclic voltammetry and impedance spectroscopy in a non-aqueous electrochemical system using ferrocene/ferrocenium (Fc/Fc+) as a redox couple, and a maximum oxidation photocurrent of 11.1 mA/cm2 was measured. GaAs NW arrays with a 36 nm layer of nickel oxide (NiO x ) synthesized by atomic layer deposition were then used as photoanodes to drive the OER. In addition to acting as an electrocatalyst, the NiO x layer served to protect the GaAs NWs from oxidative corrosion. Using this strategy, GaAs NW photoanodes were successfully used for the oxygen evolution reaction. This is the first demonstration of GaAs NW arrays for effective OER, and the fabrication and protection strategy developed in this work can be extended to study any other nanostructured semiconductor materials systems for electrochemical solar energy conversion.

Nanostructured Semiconductor Materials for Dye-Sensitized Solar Cells

Since O’Regan and Grätzel’s first report in 1991, dye-sensitized solar cells (DSSCs) appeared immediately as a promising low-cost photovoltaic technology. In fact, though being far less efficient than conventional silicon-based photovoltaics (being the maximum, lab scale prototype reported efficiency around 13%), the simple design of the device and the absence of the strict and expensive manufacturing processes needed for conventional photovoltaics make them attractive in small-power applications especially in low-light conditions, where they outperform their silicon counterparts. Nanomaterials are at the very heart of DSSC, as the success of its design is due to the use of nanostructures at both the anode and the cathode. In this review, we present the state of the art for bothn-type andp-type semiconductors used in the photoelectrodes of DSSCs, showing the evolution of the materials during the 25 years of history of this kind of devices. In the case ofp-type semiconductors, also some other energy conversion applications are touched upon.