SrTiO3-CaCr0.5Nb0.5O3 solid solutions as p-type photocatalysts for Z-scheme water splitting under visible light illumination

P-type semiconductivity has been observed in solid solution series (SrTiO3)1-x(CaCr0.5Nb0.5O3)x (0.0 ≤x ≤ 0.15),which all adopt cubic symmetry and own intense absorption in the visible light region.These solid solutions are superior H2 evolution photocatalysts under visible light illumination (λ ≥400 nm).An AQE as high as 1.02 ％ at 420 ± 20 nm has been achieved at optimal composition(SrTiO3)0.85(CaCr0.5Nb0.5O3)0.15 which significantly surpasses the parent compounds.Stoichiometric H2/O2 production under visible light illumination has been successfully realized using Z-scheme system containing (SrTiO3)0.85(CaCr0.5Nb0.5O3)0.15,WO3 and I-/IO3-redox couple.     

Effects of aluminum on the properties of p-type Cu-Al-O transparent oxide semiconductor prepared by reactive co-sputtering

p-Type Cu-Al-O films are successfully prepared by using radio frequency magnetron reactive co-sputtering deposition with Cu and Al metallic targets. Stoichiometric Cu/Al atomic percentage ratio has been achieved. The films show good transmittance in the range of 20-80% with an average thickness of 250 nm. The optical direct band gaps of the films are found in the range of 2.9-3.3 eV depending on the aluminum content. Blue-shift in absorption edge and optical band gap broadening effect are found with the increase of Al content in the films.     

Mn:SnO2 ceramics as p-type oxide semiconductor

SnO₂-based ceramics substituted with manganese as a new p-type oxide semiconductor were prepared by conventional solid state reaction. The Mn was ranged from 5 to 20 mol%, and the microstructure as well as the physical and chemical properties was characterized. Single-phase rutile of Mn:SnO₂ solid solution was obtained in all compositions. Lattice parameter was decreased with the increase of amount of Mn. The compositional change and electrical properties of the Mn:SnO₂ ceramics were confirmed by X-ray photoelectron spectroscopy and Hall effect measurement. The 5-10 mol% Mn:SnO₂ solid solutions exhibited electrically p-type behavior. The simultaneous presence of Mn²⁺, Mn³⁺ and Mn⁴⁺ states was approved and Sn⁴⁺ in Mn:SnO₂ ceramics was partially substituted with Mn³⁺ which contributes p-type behavior. SnO₂ substituted with higher contents of Mn³⁺ of 50% exhibits p-type semiconductor.     

Impurity dependent semiconductor type of epitaxial CuFeO2 (111) thin films deposited by using a pulsed laser deposition

We have prepared CuFeO₂ thin films successfully oriented to the (111) direction on amorphous glass substrates by PLD. The average grain size analyzed by SEM images is about 80-90 nm, and CuFeO₂ grains are formed to the hexagonal flat shape which means CuFeO₂ with the rhombohedral structure was hexagonally grown on the amorphous glass substrate. P-type conductivities are commonly governed by impurities of the amount of metallic Cu phase. However, it was found that the highly (111) oriented CuFeO₂ film shows insulation properties and CuFe₂O₄ phase affects the change of the type of semiconductor from p-type to n-type.     

Wide-gap layered oxychalcogenide semiconductors: Materials, electronic structures and optoelectronic properties

Applying the concept of materials design for transparent conductive oxides to layered oxychalcogenides, several p-type and n-type layered oxychalcogenides were proposed as wide-gap semiconductors and their basic optical and electrical properties were examined. The layered oxychalcogenides are composed of ionic oxide layers and covalent chalcogenide layers, which bring wide-gap and conductive properties to these materials, respectively. The electronic structures of the materials were examined by normal/inverse photoemission spectroscopy and energy band calculations. The results of the examinations suggested that these materials possess unique features more than simple wide-gap semiconductors. Namely, the layered oxychalcogenides are considered to be extremely thin quantum wells composed of the oxide and chalcogenide layers or 2D chalcogenide crystals/molecules embedded in an oxide matrix. Observation of step-like absorption edges, large band gap energy and large exciton binding energy demonstrated these features originating from 2D density of states and quantum size effects in these layered materials.     

Nanostructured tellurium semiconductor: from nanoparticles to nanorods

Selective fabrication of single crystalline tellurium nanorods of various lengths and spherical nanoparticles can be easily achieved by a simple hydrothermal reduction method. The product was characterised by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction and energy-dispersive X-ray spectroscopy techniques. It was found that when the concentration of orthotelluric acid gradually increased from 4 to 10, 20, 30 and 50?mM with other conditions controlled, the morphology of the tellurium nanocrystals gradually changed from long nanorod to shorter nanorods and eventually became spherical. Based on the experimental results, the morphology control mechanism of tellurium nanocrytals was well reasoned.     

Electronic structure and optical property of semiconductor nanocrystallites

Semiconductor nanostructures show many special physical properties associated with quantum confinement effects, and have many applications in the opto-electronic and microelectronic fields. However, it is difficult to calculate their electronic states by the ordinary plane wave or linear combination of atomic orbital methods. In this paper, we review some of our works in this field, including semiconductor clusters, self-assembled quantum dots, and diluted magnetic semiconductor quantum dots. In semiconductor clusters we introduce energy bands and effective-mass Hamiltonian of wurtzite structure semiconductors, electronic structures and optical properties of spherical clusters, ellipsoidal clusters, and nanowires. In self-assembled quantum dots we introduce electronic structures and transport properties of quantum rings and quantum dots, and resonant tunneling of 3-dimensional quantum dots. In diluted magnetic semiconductor quantum dots we introduce magnetic-optical properties, and magnetic field tuning of the effective g factor in a diluted magnetic semiconductor quantum dot.     

Capacitance and conductance-frequency characteristics of Au-Sb/p-GaSe:Gd Schottky barrier diode

The Schottky barrier height (SBH) values have been obtained from the reverse bias capacitance-voltage (C-V) characteristics of Au-Sb/p-GaSe:Gd Schottky barrier diode (SBD) in the temperature range of 180-320 K. The forward bias capacitance-frequency (C-f) and conductance-frequency (G-f) measurements of Au-Sb/p-GaSe:Gd SBD have been carried out from 0 to 1.00 V with steps of 0.05 V, whereby the energy distribution of the interface states and their relaxation time have been determined from these characteristics. It has been seen that there is a good agreement between the experimental and theoretical C-f and G-f values. Also, the capacitance values obtained from C-f measurements have shown almost a plateau up to a certain value of frequency, then, have decreased. It has been seen that the interface state density has a very small density distribution range (6.02 × 10¹⁰-6.80 × 10¹⁰ cm⁻² eV⁻¹) in the energy range of (0.21−E_v)-(1.21−E_v) eV with bias from the midgap towards the top of the valence band. The interface state density values calculated for Au-Sb/p-GaSe:Gd SBD are rather low than those given in the literature.     

Estimating the sustainable capacity of semiconductor fab workstations

The cost of a semiconductor wafer fabrication facility (i.e. ‘fab’) may be as much as five or more billion US dollars. As such it is essential to determine the capacity (e.g. in terms of ‘wafer starts per week’) of such facilities. An accurate estimate of capacity – under real world conditions – is, however, difficult to achieve. Furthermore, the method for the computation of the capacity of a semiconductor fab is significantly different from that for the capacity of workstations in more conventional, less complex factories. This is due in part to the reentrant nature of the workstations (a.k.a. ‘toolsets’) that comprise a fab's production line as well as the ubiquitous employment of operation-to-machine dedications (a.k.a. layer-to-tool qualifications) – plus the need to consider multiple products employing, perhaps, a different sequence of processing steps. In this article, the matter of workstation capacity, in general, and semiconductor fabs, in particular, is examined. A means to quickly and effectively determine the maximum theoretical capacity of a workstation is developed and illustrated – followed by a way in which the more practical maximum sustainable capacity may be estimated.     

Tunable properties of wide-band gap p-type BaCu(Ch1 − xChx′)F (Ch = S, Se, Te) thin-film solid solutions

Thin-film solid solutions of BaCu(Ch_1 − xCh_x′)F (Ch, Ch′ = S, Se, or Te) wide-band gap p-type semiconductors are obtained by pulsed laser deposition at elevated substrate temperatures from alternating layers of BaCuChF and BaCuCh′F. Adjusting the thickness of the component layers varies the relative chalcogen content, which allows tunability of the film transparency and results in a conductivity change of more than three orders of magnitude. The tunability of the physical properties makes these chalcogen-based semiconductors potentially useful for optoelectronics applications. Lattice parameters of BaCuChF calculated using density functional theory agree with those previously reported for the powders. Deviations from Vegard's law are observed in BaCu(S_1 − xSe_x)F thin films with large sulfur content.     

Model-based process capability indices: The dry-etching semiconductor case study

Process capability indices are widely used to check quality standards both at the production level and for business activity. They consider the location and the deviation from specification limits and targets. The literature contains many contributions on this topic both in the univariate and the multivariate context. Motivated by a real semiconductor case study, we discuss the role of rational subgroups and the challenge they present in the computation of capability indices, especially when data refer to lots of products. In addition, our context involves a mix of problems: unilateral specification limit, nonsymmetric distribution of the data, evidence of data from a mixture of distributions, and the need to filter one component of the mixture. After solving the previous issues and because of the peculiar characteristics of semiconductor processes based on the so called “wafers,” we contribute to the literature a proposal on how to compute capability indices in the case of heteroscedastic spatial processes. With a generalized additive model, we show that it is possible to estimate a capability surface that allows the identification of regions expected to not be fully compliant with the desired quality standards.     

Photovoltaic properties of n-type amorphous In-Ga-Zn-O and p-type single crystal Si heterojunction solar cells: Effects of Ga content

Photovoltaic properties and electronic structures of n-type amorphous In-Ga_x-Zn-O/p-type Si heterojunction solar cells (x = 1, 2, and 3) were investigated focusing on the effects of Ga content based on expectation that Ga-rich films have larger band gaps and improve open circuit voltages (V_OC) of solar cells. To know the electronic structures such as the conduction band minimums (CBMs) and the valence band maximums (VBMs) of these materials, hard x-ray photoemission spectroscopy (HX-PES) was performed. Contrary to the above expectation, the best result was obtained for x = 1 with an energy conversion efficiency of 5.3%. Although the Ga-rich films had larger optical band gaps and higher CBMs, V_OC were remained low and poorer fill factors were obtained due to larger densities of defects. The low V_OCwere partly resulted from the deep VBM levels of the Ga-rich films. The defect densities are discussed in relation also to near-VBM states and near-CBM states observed in HX-PES and subgap optical absorptions.     

Organic semiconductor-based photonic crystals for solar cell arrays: band gap and optical properties

Photonic crystals (PCs) hold great potential for designing new optical devices because of the possibility of the manipulation of light with PCs. There has been an increase in research on tuning the optical properties of PCs to design devices. We design organic semiconductor-based PC structures and calculate optical properties using the plane wave expansion method and finite-difference time-domain method in an air background for a hexagonal lattice. We showed the possibility of the solar cell arrays for a 2D PC cavity on an organic semiconductor base infiltrated with a nematic liquid crystal. E7 type has been used as a nematic liquid crystal and 4,4′-Bis[4-(diphenylamino) styryl]biphenyl as an organic semiconductor material.     

An analysis of the ceiling height requirement for a large-scale semiconductor fab

This paper proposes the proposition that the fab ceiling height may become a bottleneck for throughput in a large-scale semiconductor fab. To justify the proposition, we propose a systematic approach for the design of the fab ceiling height. In this approach, we develop a queuing network model to evaluate the cycle time performance of a fab design under a target throughput. This queuing network model is adapted from Connor et al. [1996. A queueing network model for semiconductor manufacturing. IEEE Transactions on Semiconductor Manufacturing, 9 (3), 412–427] by additionally treating the transportation facilities as finite-capacity resources. Numerical experiments were carried out. The results indicate that a large-scale fab with an inappropriate ceiling height may limit the installation of transportation capacity, which, in turn, limits the utilisation of tool capacity, and thus lowers the fab throughput that can be achieved.     

A survey of semiconductor supply chain models part I: semiconductor supply chains,strategic network design,and supply chain simulation

Supply chain management issues have become increasingly important to the semiconductor industry over the last two decades due to the global distribution of facilities and increasing numbers of firms specialising in particular stages. This series of three papers reviews the literature on modelling and analysis of the larger semiconductor supply chain. After describing the structure of semiconductor supply chains to provide context for the research efforts, we propose a classification scheme for the relevant literature. The remainder of this paper (Part I) then focuses on Strategic Network Design models for this industry, supply chain coordination through contracting and semiconductor supply chain simulation. Part II discusses Demand Planning, Inventory Management and Capacity Planning, while Part III addresses Master Planning, Production Planning and Demand Fulfilment.     

New semiconductor materials for magnetoelectronics at room temperature

Most of the semiconductor materials are diamagnetic by nature and therefore cannot take active part in the operation of the magneto electronic devices. In order to enable them to be useful for such devices a recent effort has been made to develop diluted magnetic semiconductors (DMS) in which small quantity of magnetic ion is introduced into normal semiconductors. The first known such DMS are II-VI and III-V semiconductors diluted with magnetic ions like Mn, Fe, Co, Ni, etc. Most of these DMS exhibit very high electron and hole mobility and thus useful for high speed electronic devices. The recent DMS materials reported are (CdMn)Te, (GaMn)As, (GaMn)Sb, ZnMn(or Co)O, TiMn(or Co)O etc. They have been produced as thin films by MBE and other methods. This paper will discuss the details of the growth and properties of the DMS materials and some of their applications.     

表面光电压谱(SPS)在有机半导体材料研究中的应用

简要介绍了表面光电压谱（SPS）的几种常用测试方法和测试原理，通过典型实例说明了SPS技术在研究有机半导体电子结构，有机半导体薄膜的光电性能与制备方法的关系，半导体异质结性能等方面的应用，评述了SPS技术在研究酞菁氧钛／偶氮绿丹蓝复合材料的光电性能中发现的光伏极性反新现象，展望了SPS方法在有机半导体材料光电功能研究中的应用前景。     

Evaluating capacity pooling strategy in semiconductor manufacturing: a productivity perspective study

Recently, increasing attention has been focusing on the concept of the borderless fab, which expands capacity through a manufacturing strategy rather than capital investments. In a borderless fab, the capacity of several wafer fabs is pooled, and partially completed wafers are allowed to move from one fab to another. This paper proposes a model to evaluate the potential benefits of adopting capacity pooling from the macro-viewpoint. We demonstrate our model using actual full-scale fab-level operational data, and the result reveals that capacity pooling can improve monthly capacity by 3% on average.     

Synthesis of delafossite CuAlO2 p-type semiconductor with a nanoparticle-based Cu(I) acetate-loaded boehmite precursor

Delafossite CuAlO₂ p-type nanostructured semiconductor was synthesized using boehmite (γ-AlOOH) nanorods loaded with copper(I) acetate [Cu(OAc)] as a precursor (nanoprecursor). Because Cu(OAc)-loaded γ-AlOOH nanorods are highly anisotropic, they tend to form inherent bunches consisting of several nanorods during the course of drying the nanoprecursor dispersion droplet on a solid substrate. By annealing the nanoprecursor at 1150 °C in air, a delafossite CuAlO₂ polycrystal was successfully obtained as the dominant phase. The CuAlO₂ polycrystal is found to exhibit the (1 1 0) crystal orientation. The crystalline anisotropy of CuAlO₂, which is not usually attainable using conventional molecular precursors, is presumably originated in the anisotropic morphology of the nanoprecursor. The Seebeck coefficient, resistivity and thermal conductivity of the CuAlO₂ polycrystal at 300 K were found to be +560 μV K⁻¹, 1.3 Ω m and 19.4 W K⁻¹ m⁻¹, respectively, confirming the p-type nature of the CuAlO₂ polycrystal.     

Effects of RF power variation on properties of N-doped p-type ZnO thin films grown by plasma-assisted MOCVD

High quality N-doped ZnO films were grown at different RF powers on glass substrates by plasma-assisted metalorganic chemical vapor deposition. Scanning electron microscopy, X-ray diffraction and Hall analyses were carried out to investigate the effects of RF power variation on surface morphology, crystallinity and electrical properties of the ZnO films. Increasing the RF power resulted in compacter surface morphology and change of the crystallinity as well as incorporation of more N atoms. Films grown at 150 W exhibited the best p-type electrical properties. Moreover, room temperature photoluminescence spectra showed strong emission related to N acceptor.