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Instruments / Technical Area	Publication Details	Published	Actions
I09-Surface and Interface Structural Analysis	Sn 5s2 lone pairs and the electronic structure of tin sulphides: A photoreflectance, high-energy photoemission, and theoretical investigation Leanne A. H. Jones , Wojciech M. Linhart , Nicole Fleck , Jack E. N. Swallow , Philip A. E. Murgatroyd , Huw Shiel , Thomas J. Featherstone , Matthew J. Smiles , Pardeep K. Thakur , Tien-Lin Lee , Laurence J. Hardwick , Jonathan Alaria , Frank Jaeckel , Robert Kudrawiec , Lee A. Burton , Aron Walsh , Jonathan M. Skelton , Tim D. Veal , Vin R. Dhanak Physical Review Materials 4 DOI: 10.1103/PhysRevMaterials.4.074602 Diamond Proposal Number(s): [21431] Open Access Show Abstract ▼ Abstract: The effects of Sn 5 s lone pairs in the different phases of Sn sulphides are investigated with photoreflectance, hard x-ray photoemission spectroscopy (HAXPES), and density functional theory. Due to the photon energy-dependence of the photoionization cross sections, at high photon energy, the Sn 5 s orbital photoemission has increased intensity relative to that from other orbitals. This enables the Sn 5 s state contribution at the top of the valence band in the different Sn-sulphides, SnS, Sn 2 S 3 , and SnS 2 , to be clearly identified. SnS and Sn 2 S 3 contain Sn(II) cations and the corresponding Sn 5 s lone pairs are at the valence band maximum (VBM), leading to ∼ 1.0 –1.3 eV band gaps and relatively high VBM on an absolute energy scale. In contrast, SnS 2 only contains Sn(IV) cations, no filled lone pairs, and therefore has a ∼ 2.3 eV room-temperature band gap and much lower VBM compared with SnS and Sn 2 S 3 . The direct band gaps of these materials at 20 K are found using photoreflectance to be 1.36, 1.08, and 2.47 eV for SnS, Sn 2 S 3 , and SnS 2 , respectively, which further highlights the effect of having the lone-pair states at the VBM. As well as elucidating the role of the Sn 5 s lone pairs in determining the band gaps and band alignments of the family of Sn-sulphide compounds, this also highlights how HAXPES is an ideal method for probing the lone-pair contribution to the density of states of the emerging class of materials with n s 2 configuration.	Jul 2020
	Band gap dependence on cation disorder in ZnSnN2 solar absorber Tim D. Veal , Nathaniel Feldberg , Nicholas Quackenbush , Wojciech M. Linhart , David O. Scanlon , Louis Piper , Steven M. Durbin Advanced Energy Materials 5 (24) DOI: 10.1002/aenm.201501462 Open Access Show Abstract ▼ Abstract: The band gap of earth-abundant ZnSnN2 can be tuned between 1 and 2 eV by varying the growth conditions and resulting cation disorder. The optical absorption edges and carrier densities fall between model curves for cation-ordered orthorhombic and disordered wurtzite ZnSnN2. Hard X-ray photoemission spectra suggest different degrees of cation disorder from comparison with hybrid DFT-calculated densities of states.	Dec 2015

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I09-Surface and Interface Structural Analysis

Sn 5s2 lone pairs and the electronic structure of tin sulphides: A photoreflectance, high-energy photoemission, and theoretical investigation