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Instruments / Technical Area	Publication Details	Published
I09-Surface and Interface Structural Analysis	Experimental and theoretical investigation of the chemical exfoliation of Cr-based MAX phase particles Minh Hai Tran , Ali M. Malik , Michael Dürrschnabel , Anna Regoutz , Pardeep Thakur , Tien-lin Lee , Delwin Perera , Leopoldo Molina-luna , Karsten Albe , Jochen Rohrer , Christina S. Birkel Dalton Transactions 13 DOI: 10.1039/D0DT01448F Diamond Proposal Number(s): [24670] Show Abstract ▼ Abstract: Two-dimensional carbides/nitrides, typically called MXenes, are an emerging member of the ever-growing family of two-dimensional materials. The prediction of a ferromagnetic groundstate in chromium-containing MXenes has triggered growing interest in their chemical exfoliation from Cr-based MAX phases. However, the exfoliation poses serious difficulties using standard etching agents such as hydrofluoric acid (HF). Here, we investigate the exfoliability of Cr2GaC particles by chemical etching with aqueous HF both experimentally and theoretically. Structural and microstructural analyses show that the Cr2GaC particles decompose into chromium carbide and oxide without the formation of a Cr-based MXene. A thermodynamic analysis based on ab initio electronic structure calculations reveals that the exfoliation of Cr-based MXene from Cr2GaC by HF-etching is inhibited by more favorable competing reactions. This result confirms the experimental finding and suggests that HF is an unsuitable etching agent for a successful exfoliation of Cr2GaC.	Jul 2020
B16-Test Beamline Optics	Nanofocusing optics for synchrotron radiation made from polycrystalline diamond Oliver Fox , Lucia Alianelli , A. M. Malik , Ian Pape , P. W. May , Kawal Sawhney Optics Express 22 (7) DOI: 10.1364/OE.22.007657 PMID: 24718141 Diamond Proposal Number(s): [5870] Open Access Show Abstract ▼ Abstract: Diamond possesses many extreme properties that make it an ideal material for fabricating nanofocusing x-ray optics. Refractive lenses made from diamond are able to focus x-ray radiation with high efficiency but without compromising the brilliance of the beam. Electron-beam lithography and deep reactive-ion etching of silicon substrates have been used in a transfer-molding technique to fabricate diamond optics with vertical and smooth sidewalls. Latest generation compound refractive lenses have seen an improvement in the quality and uniformity of the optical structures, resulting in an increase in their focusing ability. Synchrotron beamline tests of two recent lens arrays, corresponding to two different diamond morphologies, are described. Focal line-widths down to 210 nm, using a nanocrystalline diamond lens array and a beam energy of E = 11 keV, and 230 nm, using a microcrystalline diamond lens at E = 15 keV, have been measured using the Diamond Light Source Ltd. B16 beamline. This focusing prowess is combined with relatively high transmission through the lenses compared with silicon refractive designs and other diffractive optics.	Mar 2014
B16-Test Beamline Optics	Deep reactive ion etching of silicon moulds for the fabrication of diamond x-ray focusing lenses A. M. Malik , O. J. L. Fox , L. Alianelli , A. M. Korsunsky , R. Stevens , I. M. Loader , M. C. Wilson , Ia. Pape , K. J. S. Sawhney , P. W. May Journal Of Micromechanics And Microengineering 23 (12), 7778-7788 DOI: 10.1088/0960-1317/23/12/125018 Diamond Proposal Number(s): [2096] Open Access Show Abstract ▼ Abstract: Diamond is a highly desirable material for use in x-ray optics and instrumentation. However, due to its extreme hardness and resistance to chemical attack, diamond is difficult to form into a structure suitable for x-ray lenses. Refractive lenses are capable of delivering x-ray beams with nanoscale resolution. A moulding technique for the fabrication of diamond lenses is reported. High-quality silicon moulds were made using photolithography and deep reactive ion etching. The study of the etch process conducted to achieve silicon moulds with vertical sidewalls and minimal surface roughness is discussed. Issues experienced when attempting to deposit diamond into a high-aspect-ratio mould by chemical vapour deposition are highlighted. Two generations of lenses have been successfully fabricated using this transfer-moulding approach with significant improvement in the quality and performance of the optics observed in the second iteration. Testing of the diamond x-ray optics on the Diamond Light Source Ltd synchrotron B16 beamline has yielded a line focus of sub-micrometre width.	Dec 2013

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