Investigation of pre-structured GaAs surfaces for subsequent site-selective InAs quantum dot growth

In this study, we investigated pre-structured (100) GaAs sample surfaces with respect to subsequent site-selective quantum dot growth. Defects occurring in the GaAs buffer layer grown after pre-structuring are attributed to insufficient cleaning of the samples prior to regrowth. Successive cleaning steps were analyzed and optimized. A UV-ozone cleaning is performed at the end of sample preparation in order to get rid of remaining organic contamination

A Horizon Scan to Support Chemical Pollution–Related Policymaking for Sustainable and Climate-Resilient Economies

Data Availability Statement: All data are included in the Supporting Information for publication online.Supporting Information is available online at https://setac.onlinelibrary.wiley.com/doi/10.1002/etc.5620#support-information-section .Copyright © 2023 Crown copyright and The Authors. While chemicals are vital to modern society through materials, agriculture, textiles, new technology, medicines, and consumer goods, their use is not without risks. Unfortunately, our resources seem inadequate to address the breadth of chemical challenges to the environment and human health. Therefore, it is important we use our intelligence and knowledge wisely to prepare for what lies ahead. The present study used a Delphi-style approach to horizon-scan future chemical threats that need to be considered in the setting of chemicals and environmental policy, which involved a multidisciplinary, multisectoral, and multinational panel of 25 scientists and practitioners (mainly from the United Kingdom, Europe, and other industrialized nations) in a three-stage process. Fifteen issues were shortlisted (from a nominated list of 48), considered by the panel to hold global relevance. The issues span from the need for new chemical manufacturing (including transitioning to non-fossil-fuel feedstocks); challenges from novel materials, food imports, landfills, and tire wear; and opportunities from artificial intelligence, greater data transparency, and the weight-of-evidence approach. The 15 issues can be divided into three classes: new perspectives on historic but insufficiently appreciated chemicals/issues, new or relatively new products and their associated industries, and thinking through approaches we can use to meet these challenges. Chemicals are one threat among many that influence the environment and human health, and interlinkages with wider issues such as climate change and how we mitigate these were clear in this exercise. The horizon scan highlights the value of thinking broadly and consulting widely, considering systems approaches to ensure that interventions appreciate synergies and avoid harmful trade-offs in other areas. We recommend further collaboration between researchers, industry, regulators, and policymakers to perform horizon scanning to inform policymaking, to develop our ability to meet these challenges, and especially to extend the approach to consider also concerns from countries with developing economies. Environ Toxicol Chem 2023;00:1–17. © 2023 Crown copyright and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article is published with the permission of the Controller of HMSO and the King's Printer for Scotland.Department for Environment, Food and Rural Affair

A Horizon Scan to Support Chemical Pollution–Related Policymaking for Sustainable and Climate‐Resilient Economies

While chemicals are vital to modern society through materials, agriculture, textiles, new technology, medicines, and consumer goods, their use is not without risks. Unfortunately, our resources seem inadequate to address the breadth of chemical challenges to the environment and human health. Therefore, it is important we use our intelligence and knowledge wisely to prepare for what lies ahead. The present study used a Delphi‐style approach to horizon‐scan future chemical threats that need to be considered in the setting of chemicals and environmental policy, which involved a multidisciplinary, multisectoral, and multinational panel of 25 scientists and practitioners (mainly from the United Kingdom, Europe, and other industrialized nations) in a three‐stage process. Fifteen issues were shortlisted (from a nominated list of 48), considered by the panel to hold global relevance. The issues span from the need for new chemical manufacturing (including transitioning to non‐fossil‐fuel feedstocks); challenges from novel materials, food imports, landfills, and tire wear; and opportunities from artificial intelligence, greater data transparency, and the weight‐of‐evidence approach. The 15 issues can be divided into three classes: new perspectives on historic but insufficiently appreciated chemicals/issues, new or relatively new products and their associated industries, and thinking through approaches we can use to meet these challenges. Chemicals are one threat among many that influence the environment and human health, and interlinkages with wider issues such as climate change and how we mitigate these were clear in this exercise. The horizon scan highlights the value of thinking broadly and consulting widely, considering systems approaches to ensure that interventions appreciate synergies and avoid harmful trade‐offs in other areas. We recommend further collaboration between researchers, industry, regulators, and policymakers to perform horizon scanning to inform policymaking, to develop our ability to meet these challenges, and especially to extend the approach to consider also concerns from countries with developing economies

Oxidation and sulfur passivation of GaInAsP(100)

The quaternary III\u2013V compound semiconductor GaInAsP is an important material for many optoelectronic devices, the surface of which generally needs to be passivated in the fabrication of such devices. Thus understanding the surface chemistry and monitoring the surface band gap states after oxidation and sulphur passivation have become necessary. Further, understanding the effect of ion bombardment on the GaInAsP surface during dielectric deposition is also of importance for device fabrication. In this study, quaternary GaInAsP(100) surfaces were subjected to UV/ozone and wet chemical treatments, dilute HF etching, sulfur passivation, and Ar ion bombardment. The composition and the relative movement of the surface Fermi level (EFs) of the surfaces were measured by x-ray photoemission spectroscopy (XPS) after oxidation, HF etching, sulfur passivation, and ion bombardment of surfaces. It was found that oxidation by ozone exposure formed multiple oxide phases of all the constituent elements. Both HF etching and sulfur passivation treatments were effective in generating surfaces having almost no oxide. It was also found that while sulfur passivation combined with an ultrahigh vacuum annealing at 300\u2009\ub0C reduced the surface band bending on n-type GaInAsP(100), it inverted p-type GaInAsP to n-type. An L-edge absorption spectrum of the sulfur passivated surface confirmed the presence of a sulfur layer. Further, it was found that an Ar+ ion bombardment pins the EFs near the midgap for both n- and p-type GaInAsP surfaces.Peer reviewed: YesNRC publication: Ye

A role for Haemophilus ducreyi Cu,ZnSOD in resistance to heme toxicity

The Cu,Zn superoxide dismutase (Cu,ZnSOD) from Haemophilus ducreyi is the only enzyme of this class which binds a heme molecule at its dimer interface. To explore the role of the enzyme in this heme-obligate bacterium, a sodC mutant was created by insertional inactivation. No difference in growth rate was observed during heme limitation. In contrast, under heme rich conditions growth of the sodC mutant was impaired compared to the wild type strain. This growth defect was abolished by supplementation of exogenous catalase. Genetic complementation of the sodC mutant in trans demonstrated that the enzymatic property or the heme-binding activity of the protein could repair the growth defect of the sodC mutant. These results indicate that Cu,ZnSOD protects Haemophilus ducreyi from heme toxicity

Diffusion of neodymium into sputtered films of tantalum pentoxide

In this communication the diffusion of neodymium into rf-sputtered films of tantalum pentoxide (Ta2O5) has been investigated using the SIMS technique. The diffusion characteristics were obtained for a temperature of 1100°C, and the results showed a time-dependent diffusion coefficient that reflects a transition of the sputtered films from the amorphous to the crystalline phase. The potential for doping films of Ta2O5 with neodymium by diffusion, for the realization of novel active optical devices, is also discussed.<br/

Passivation of the SiNx/GaAs (110) interface

Not AvailableNRC publication: Ye

Structure of the SiN[sub x]/GaAs (110) interface modified with ultrathin Si and sulfur passivation

The SiNx/GaAs (110) interface structure of the metal-insulator-semiconductor (MIS) capacitors modified with ultrathin Si or Si/Ge (5 to 15 \uc5) heterolayers and sulfur passivation were studied by capacitance-voltage (CV) measurements, high resolution medium energy ion scattering and extended x-ray absorption fine structure with synchrotron radiation. The results showed that Si/S multilayer passivation can improve the interface properties of the MIS capacitors made on n-type GaAs (110). The element depth profiling in a subnanometer scale and the atomic structure measurements showed that a Si or Si/Ge heterolayer on sulfur passivated GaAs (110) can substantially limit Ga(As) precipitation at the interface but cannot completely suppress the incorporation of Ga(As) into the Si heterolayer. These results can be used to interpret the observed CV characteristics of the capacitors and to understand the limitation of the passivation approach.NRC publication: Ye