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Sample rotation during depth profiling

The aim of this investigation was to characterise the performance of the gas-cluster ion source (GCIS) for the depth profiling of thick organic multi-layer materials. The sample is composed of 25 repeating units of polystyrene (PS) and polyvinylpyrrolidine (PVP) PS = 288 ± 1.3 and PVP = 328 ± 7 nm on a glass substrate. It has been considered challenging to depth profile thick samples (>1 micron) of soft materials due to the changes which occur under sus-tained X-ray irradiation and bombardment of charged projectiles, however, in this study we describe a methodology to eliminate these issues. The use of fast acquisition, snapshot spectroscopy and sample rotation during etching is presented.

A Multi-Technique Characterization of Polymer Materials with XPS, UPS and REELS

Using a combination of surface analysis tools, different polymer materials were analysed using the Kratos AXIS Supra+. A common issue with XPS analysis is that the C 1s envelope can look relatively similar for different polymer materials, making them difficult to distinguish using XPS alone. Plasmon features, such as the π-π* transition, which give information related to the sp2 content of a material are also concealed by shifts between different C chemical states. Here, a combination of XPS, UPS and REELS are used as complimentary tools to help understand the chemistry of several polymer materials.


XPS and UPS Characterization of a Hybrid PbBr Perovskite Material with Work Function Measurement

UPS analysis of (semi)conducting samples allows the measurement of the work function of a material. Combined with XPS, this is a powerful combination of techniques to gain information about the valence structure of the surface. Here, a thin film, hybrid organic-inorganic lead bromide perovskite is analysed using a Kratos AXIS spectrometer. A comparison of the data is made after the removal of adventitious carbon with the Gas Cluster Ion Source (GCIS) to interpret how the work function of the material is affected.

Reconstructed Concentration Depth Profiles from Angle-Resolved XPS using MEM Software

XPS was used to characterize the surface chemistry of layered thin film materials, using monochromated Al Kα (1486.6 eV) X-rays to gain quantitative chemical information from the uppermost 10 nm of the surface. In this study, we illustrate how ARXPS is used as a more surface sensitive approach to probe only the topmost 1-3 nm of a material, and how one can utilize Maximum Entropy Method (MEM) software to recreate a concentration depth profile from the resulting data. How the re-moval of contamination effects the resulting MEM model fit is also explored following gentle sputter cleaning using the GCIS.

ES300 Electron Spectrometer - specification

In late 1975 a special UHV XPS instrument incorporating many novel features was supplied to the UK Central Energy Generation Board (CEGB).  This instrument was further developed into the latest electron spectrometer, the ES300, which was produced with excitation sources and vacuum pumping according to a customer's individual requirements.  A comprehensive data system DS-300 was also launched with the ES300.

From these specifications we can see that unlimate performance of the ES300 was defined as 20,000 cps at 0.92 eV FWHM for the Ag 3d5/2 peak.


Distribution, segregation and chemical state identification of Lithium salts on Cu electrodes

Rechargeable metal-based batteries (Li, Na and Al) are among the most versatile platforms for high-energy storage. Unfortunately however there are several pitfalls for these energy storage systems, one of which is deposition and dendrite formation during repeated cycles of charge and discharge. Many studies have been performed in search of a dendrite-free, deposition-free system for lithium batteries using novel materials such as 3D structures and carbon nanofibers.[1,2]  Here we will explore the distribution of Lithium in different chemical environments on electrode surfaces. We employ conventional surface analysis techniques (XPS) to yield large area, quantitative, information regarding the distribution of surface species. To explore the lateral and depth distribution of Li we also utilise XP imaging and Argon cluster depth profiling.

Surface analysis of strip coated materials pre- and post- 'cleaning'

Strip coating materials are commonly used in optic applications for the removal of grease and small particulates form the surfaces of delicate materials. Typically these include mask gratings, laser optics, telescope lenses and refractors. A clear red solution consisting of a blend of polymers is applied using a small brush and is then left to set. Once set, the polymer coating is peeled away leaving a pristine surface free of particulates.

Quantification of layer composition in compound semiconductors

Compound semiconductors are the key underpinning technology in optoelectronics, and also used in electronic applications with specialist requirements (e.g. power). The ability to engineer the electronic and optical properties of compound semiconductor alloys, for example in terms of their alloy composition, which may be binary, ternary, quaternary or quinary, and grow multiple layers of different semiconductor alloys on top of each other (heterostructures), is a key part of their success.

Excellent and extreme examples of this are devices that contain distributed Bragg reflectors: alternating layers of high- and low refractive-index material (typically GaAs/AlxGa1-xAs) to create a stop-band where a very particular set of wavelengths are almost fully reflected (ideally over 99.9%). For example, vertical cavity surface emitting lasers (VCSELs) are tiny (low-cost) semiconductor lasers that use a pair of DBRs to form the mirrors of the lasing cavity. In VCSELs, the quality and consistency of the DBRs is important, as a VCSEL has a gain length on average 105 times smaller than an edge-emitting laser, and therefore needs ultra-high reflectivity mirrors to achieve a reasonable threshold current. Examples of other, emerging, devices that use DBRs are single photon LEDs (SPLEDs); these are needed for quantum key distribution in quantum cryptography networks. This study focuses on these DBRs, and methods to accurately characterise their structure, including determining whether the semiconductor layer growth has proceeded as desired. X-ray photoelectron spectroscopy (XPS) depth profiles are taken to measure the chemical composition of the DBR layers to further characterise the growth. Even a small change in Al composition affects the refractive index, thus changing the optical path length of the layer, with consequences for everything from mirror characteristics to laser output wavelength. XPS yields quantitative information regarding Al content for the DBR structure, which directly relates to device performance.