The tuning of structural, optical, and electrical properties of Al-doped ZnO films deposited by atomic layer deposition technique is reported in this work. With the increasing Al doping level, the evolution from (002) to (100) diffraction peaks indicates the change in growth mode of ZnO films. Spectroscopic ellipsometry has been applied to study the thickness, optical constants, and band gap of AZO films. Due to the increasing carrier concentration after Al doping, a blue shift of band gap and absorption edge can be observed, which can be interpreted by Burstein-Moss effect. The carrier concentration and resistivity are found to vary significantly among different doping concentration, and the optimum value is also discussed. The modulations and improvements of properties are important for Al-doped ZnO films to apply as transparent conductor in various applications.

We present an experimental study on the influence of sub-stoichiometric WO_3−x phase upon gas sensing performance. Our work shows that the sub-stoichiometric WO_3−x can be used to enhance the low temperature sensing performance.

In this work, the high crystalline copper oxide (CuO) nanoparticles were fabricated by a hydrothermal method, and their structural properties were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The sensing results show that CuO nanoparticles exhibit enhanced sensitivity and good selectivity for hydrogen sulfide (H₂S) gas at a low temperature. There are two working mechanisms involved in the H₂S sensing based on CuO nanoparticle sensors. They are the H₂S oxidation mechanism and the copper sulphide (CuS) formation mechanism, respectively. The two sensing mechanisms collectively enhance the sensor’s response in the H₂S sensing process. The Cu–S bonding is stable and cannot break spontaneously at a low temperature. Therefore, the CuS formation inhibits the sensor’s recovery process. Such inhibition gradually enhances as the gas concentration increases from 0.2 ppm to 5 ppm, and it becomes weaker as the operating temperature rises from 40 °C to 250 °C. The XPS results confirmed the CuS formation phenomenon, and the micro Raman spectra demonstrated that the formation of CuS bonding and its decomposition can be effectively triggered by a thermal effect. Gas-sensing mechanism analysis supplied abundant cognition for the H₂S sensing phenomena based on CuO materials.

WO₃·nH₂O microcrystals with different shapes have been synthesized via a facile inorganic hydrothermal route. By controlling the amount of Na₂SO₄ in the precursor solution, hexagonal WO₃·0.33H₂O nanoplates, WO₃ nanorods, and octahedron-shaped WO₃·0.5H₂O crystals have been obtained, highlighting the role of Na₂SO₄ in the growth of WO₃·nH₂O crystals. Based on the experimental observations, we have discussed the growth mechanisms of the WO₃·nH₂O crystals. The adsorption ability and photocatalytic activities of tungsten trioxide hydrates have also been investigated, and the results show that the WO₃·0.33H₂O nanoplates with large surface areas show the largest adsorption ability, and WO₃·0.5H₂O octahedral microcrystals with large bare crystal face exhibit the highest photodegradation performance in these samples, rendering their potential application in the treatment of organic pollutants.

Acquiring multi-dimensional optical information, such as intensity, spectrum, polarization, and phase, can significantly enhance the performance of photodetectors. Incorporating these dimensions allows for improved image contrast, enhanced recognition capabilities, reduced interference, and better adaptation to complex environments. However, the challenge lies in obtaining these dimensions on a single photodetector. Here we propose a misaligned unipolar barrier photodetector based on van der Waals heterojunction to address this issue. This structure enables spectral detection by switching between two absorbing layers with different cut-off wavelengths for dual-band detection. For polarization detection, anisotropic semiconductors like black phosphorus and black arsenic phosphorus inherently possess polarization-detection capabilities without additional complex elements. By manipulating the crystal direction of these materials during heterojunction fabrication, the device becomes sensitive to incident light at different polarization angles. This research showcases the potential of the misaligned unipolar barrier photodetector in capturing multi-dimensional optical information, paving the way for next-generation photodetectors.

Thermal radiation with narrow bandwidth and well-defined emission directions is highly sought after for a variety of applications, ranging from infrared sensing and thermal imaging to thermophotovoltaics. Here, a large-area (4-inch-diameter) long-wavelength infrared thermal emitter is presented, which is spectrally selective, highly directional, and easily fabricated. The basic structure of the proposed thermal emitter is composed of a truncated one-dimensional photonic crystal and a continuous metallic film separated by a dielectric spacer. Experimental results show that the emitter exhibits a narrowband thermal emittance peak of 92% in the normal direction at the wavenumber of 943.4 cm⁻¹ with a bandwidth of 12.5 cm⁻¹ and a narrow angular emission lobe with a limited solid angle of 0.325 sr (0.115 sr) for s (p) polarization. Numerical simulation analyses are performed to corroborate the experimental observations. Temporal coupled-mode theory combined with transfer matrix method is employed to analytically investigate the emission properties of the structure, which not only can be used to understand the experimental results, but also plays a certain guidance role in designing a thermal emitter with the desired properties. The present thermal emitter can be implemented for thermal photonics management, allowing applications in thermal imaging and medical systems, etc.