Applications of AES, XPS and TOF SIMS to phosphor materials † H. C. Swart, a * J. J. Terblans, a O. M. Ntwaeaborwa, a R. E. Kroon, a E. Coetsee, a I. M. Nagpure, a Vijay Kumar, a Vinod Kumar a and Vinay Kumar a,b The important role of Auger electron spectroscopy (AES), X-ray photo electron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (TOF-SIMS) to characterize different phosphor materials is pointed out with examples. AES is used to monitor surface reactions during electron bombardment and also to determine the elemental composition of the surfaces of the materials, while XPS and TOF-SIMS are used for the surface chemical composition and valence state of the dopants. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: AES; XPS; TOF-SIMS Introduction Phosphor materials are an integral part of our daily life. Lumines- cent compounds and materials have numerous uses, most notably in detectors of various sorts, but also in consumer products such as displays, light emitting diode (LED) lighting and watches. [1–3] The emission properties, whether of a fast decay rate fluorescent material or a slow decay rate phosphorescent material, are defined by the chemical composition and the physical structure of the luminescent material. [1] Phosphor hosts, defects, dopant concen- tration and valence state are some of the important parameters to be considered when designing new phosphor materials. [4–7] The crystal field that is determined by the environment in the host material in combination with the dopant ion with the correct va- lence state can be used to obtain emissions from the UV to the IR wavelength ranges. The stability of these phosphors under electron or photon irradiation is important for the flat panel display market. Surface characterization techniques play a vital role in the complete understanding of the luminescent properties of phosphor mate- rials. Auger electron spectroscopy (AES), X-ray photo electron spec- troscopy (XPS) and time of flight secondary ion mass spectrometry (TOF-SIMS) are used to characterize different phosphor materials. The important role of these techniques is illustrated in this paper. Experimental setup Phosphor materials were prepared with different synthesis methods such as chemical bath deposition (CBD), [8] sol–gel, [5,7] combustion, [4] etc. Surface characterization of these phosphors was carried out with a PHI 700 Auger Nanoprobe unit to obtain both scanning Auger and electron microscopy (SAM and SEM) micrographs. Images were captured with a 25 kV, 10 nA electron beam. The cathodoluminescence (CL) intensity degradation studies were carried out using AES coupled with a CL spectrometer. The PHI (model 549) Auger spectrometer and S2000 Ocean Optics spectrometer were simultaneously used to collect the Auger and CL data, respectively. The primary electron beam current was typi- cally 10 μA. The Auger and CL data were collected in a vacuum chamber with a base pressure in the 10 À9 Torr range and the chamber backfilled with oxygen to 10 À6 Torr. Throughout the experiment, the Auger and CL data were recorded using the same primary electron beam of 2 keV. The decrease of the CL intensities during prolonged electron bombardment of the phosphors was monitored continuously for periods up to 24 h at the different pressures. The changes in intensity of the different CL peaks and Auger peak to peak heights (APPH) were monitored. The XPS data were collected before and after degradation to evaluate the chemical composition and electronic states of the different elements. The data were collected using the PHI 5000 Versa probe-Scanning ESCA microprobe. A low energy Ar + ion gun and low energy neutralizer electron gun were used to minimize charging on the surface. Monochromatic Al K α radiation (hν = 1486.6 eV) was used as the excitation source. A 25 W, 15 kV electron beam was used to excite the X-ray beam of 100 μm diameter that was used to analyze the different binding energy peaks (pass energy 11 eV, analyzer resolution ≤0.5 eV). Multipack version 8.2 software [9] was used to analyze the chemical elements and their electronic states using Gaussian–Lorentz fits. The valence state and site positions of the dopants were also confirmed with XPS. TOF-SIMS measurements were performed on a PHI TRIFT V nanoTOF. A pulsed 30 keV Au + primary ion beam, operated at a DC current of 100 pA, was used to acquire chemical images of the phosphor in both the positive and the negative secondary ion polarities. The analytical field of view was 200 μm × 200 μm with a 256 pixel × 256 pixel digital raster, and the primary ion dose was maintained well within the static limit, i.e. ≤1.2 × 10 11 Au + /cm 2 , for each analysis. Charge compensation was achieved with a dual-beam (≤15 eV e À and ≤10eV Ar + ) charge neutralizer. A raw data stream file was collected to allow full post- acquisition evaluation (i.e. retrospective analysis) of the data. * Correspondence to: H. Swart, Physics, University of the Free State, P.O. Box 339, Bloemfontein, ZA9300, South Africa. E-mail: swarthc@ufs.ac.za † Paper published as part of the ECASIA 2013 special issue. a Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300, South Africa b School of Physics, Shri Mata Vaishno Devi University, Katra (J&K)-182320, India Surf. Interface Anal. (2014) Copyright © 2014 John Wiley & Sons, Ltd. ECASIA special issue paper Received: 23 August 2013 Revised: 22 October 2013 Accepted: 18 December 2013 Published online in Wiley Online Library (wileyonlinelibrary.com) DOI 10.1002/sia.5393