A Study of Potassium Dihydrogen Phosphate „KDP… Crystal Surfaces by XPS Mark Engelhard PNNL Environmental Molecular Sciences Laboratory, 3335 Q Avenue, Richland, WA 99352 Cheryl Evans, T. A. Land, and A. J. Nelson Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 Potassium dihydrogen phosphate KH 2 PO 4 KDP is a transparent dielectric material best known for its nonlinear optical and electro-optical properties Refs. 1 and 2. Because of its nonlinear optical properties, it has been incorporated into various laser systems for harmonic generation and optoelectrical switching. In addition, KDP is particularly suitable for use in large-aperture laser systems such as that located at the National Ignition Facility NIF because it can be grown as a single crystal to large size Refs. 3 and 4. Despite the importance of this material, surface composition and surface electronic structure data were found to be nonexistent. X-ray photoemission spectroscopy was thus used to characterize the composition and surface structure of 100 and 101 native crystals. © 2001 American Vacuum Society. DOI: 10.1116/11.20010702 Keywords: XPS; ESCA; x-ray photoelectron spectroscopy; potassium dihydrogen phosphate; KDP; orthophosphate PACS: 79.60.Bm, 68.35.Dv, 42.70.Mp Accession #s 00644, 00645 Technique: XPS Host Material: #00644: KDP (100); #00645: KDP (101) Instrument: Physical Electronics, Incorporated Quantum 2000 Major Elements in Spectrum: K, O, P Minor Elements in Spectrum: C Printed Spectra: 36 Spectra in Electronic Record: 42 Spectral Category: comparison Original Submission: 7/13/2001 Accepted for Publication: 10/15/2001 SPECIMEN DESCRIPTION (Accession #00644) Host Material: KDP 100 CAS Registry #: 7778-77-0 Host Material Characteristics: homogeneous; solid; single crys- tal; dielectric; inorganic compound Chemical Name: orthophosphate, di-H Source: Lawrence Livermore National Laboratory Host Composition: KH 2 PO 4 Form: 6 mm  3.5 mm  2 mm crystal Structure: tetragonal 100 face History & Significance: The KDP crystals were grown at Lawrence Livermore National Laboratory. As Received Condition: The crystal was received unannealed with a native oxide. Analyzed Region: 1400 m x, 200 m y Ex Situ PreparationÕMounting: The KDP crystals were rinsed with a small amount of DI water in order to remove as much surface adventitious carbon contamination as possible. The crystals were mounted onto a sample platen using a small piece of double-stick tape and then introduced into the vacuum sys- tem via a rapid pumpdown sample introduction chamber. In Situ Preparation: None Pre-Analysis Beam Exposure: Analysis began within 10 min of sample rinsing. Charge Control: Both low energy electrons and ions were used to control the surface potential. Low energy electrons 1 eV at 23 A were produced using a BaO filament and covered 1 cm 2 of the sample. Low energy Ar + ions 8 eV at 30 nA were produced in the ion gun and covered a larger area. Temp. During Analysis: 298 K Pressure During Analysis: 6.710 -7 Pa SPECIMEN DESCRIPTION (Accession #00645) Host Material: KDP 101 CAS Registry #: 77788-77-0 Host Material Characteristics: homogeneous; solid; single crys- tal; dielectric; inorganic compound Chemical Name: orthophosphate, di-H Source: Lawrence Livermore National Laboratory Host Composition: KH 2 PO 4 Form: 5 mm  4 mm  5 mm crystal Structure: tetragonal 101 face History & Significance: The KDP crystals were grown at Lawrence Livermore National Laboratory. As Received Condition: The KDP crystal was received unan- nealed with a native oxide. Analyzed Region: 1400 m x, 200 m y Ex Situ PreparationÕMounting: The KDP crystals were rinsed with a small amount of DI water in order to remove as much surface adventitious carbon contamination as possible. The crystals were mounted onto a sample platen using a small piece of double-stick tape and then introduced into the vacuum sys- tem via a rapid pumpdown sample introduction chamber. In Situ Preparation: none Pre-Analysis Beam Exposure: Analysis began within 10 min of sample rinsing. Charge Control: Both low energy electrons and ions were used to control the surface potential. Low energy electrons 1 eV at 23 A were produced using a BaO filament and covered 1 cm 2 of the sample. Low energy Ar + ions 8 eV at 30 nA were produced in the ion gun and covered a larger area. Temp. During Analysis: 298 K Pressure During Analysis: 6.710 -7 Pa 56 Surface Science Spectra, Vol. 8, No. 1, 2001 1055-5269/2001/8(1)/56/25/$18.00 © 2001 American Vacuum Society