Laser desorption ionization time-of-flight mass spectrometry of erbium-doped Ga-Ge-Sb-S glasses.

RATIONALE: Rare earth-doped sulphide glasses in the Ga-Ge-Sb-S system present radiative emissions from the visible to the middle infrared range (mid-IR) range, which are of interest for a variety of applications including (bio)-chemical optical sensing, light detection, and military counter-measures. The aim of this work was to reveal structural motifs present during the fabrication of thin films by plasma deposition techniques as such knowledge is important for the optimization of thin film growth. METHODS: The formation of clusters in plasma plume from different concentrations of erbium-doped Ga5Ge20Sb10S65 glasses (0.05, 0.1, and 0.5 wt. % of erbium) using laser (337 nm) desorption ionization (LDI) was studied by time-of-flight mass spectrometry (TOF MS) in both positive and negative ion mode. The stoichiometry of the Ga(m)Ge(n)Sb(o)S(p)(+/-) clusters was determined via isotopic envelope analysis and computer modelling. RESULTS: Several Ga(m)Ge(n)Sb(o)S(p)(+/-) singly charged clusters were found but, surprisingly, only four species (Sb3S4(+/-), GaSb2S(p)(+/-) (p = 4, 5), Ga3Sb2S7(+/-) ) were common to both ion modes. For the first time, species containing rare earths (GaSb2SEr(+) and GaS6 Er2(+)) were identified in the plasma formed from rare earth-doped chalcogenide glasses, directly confirming the importance of gallium presence for rare earth bonding within the glassy matrix. CONCLUSIONS: The local structure of Ga-Ge-Sb-S glasses is at least partly different from the structure of species identified in plasma by mass spectrometry, as deduced from Raman scattering spectroscopy analysis; these glasses are mainly formed by [GeS4/2]/[GaS4/2] tetrahedra and [SbS3/2] pyramids. Extended X-ray absorption fine structure measurements show that Er(3+) ions in Ga-Ge-Sb-S glasses are surrounded by 7 sulphur atoms.

Laser ablation synthesis of new phosphorus nitride clusters from α-P3N5 via Laser Desorption Ionization and Matrix Assisted Laser Desorption Ionization Time-Of-Flight Mass Spectrometry.

Phosphorus nitride clusters generated during Laser Desorption Ionization (LDI) and Matrix-Assisted Laser Desorption Ionization (MALDI) of solid P(3) N(5) were analyzed via Time-of-Flight Mass Spectrometry (TOF MS). The LDI TOF mass spectra show the formation of series of clusters: P(m)N(n)(+) {(m=1; n=8-11), (m=4; n=3-4), (m=5; n=1-5), (m=6; n=1-3, 5-8), (m=2-7; n=1), (m=5-10; n=2), (m=4-6; n=3), (m=4,5; n=4), (m=5,6; n=5)}, and P(m)N(n)(-) (m=4,5; n=1). Using 3-hydroxypicolinic acid (HPA) as a matrix the P(m)N(n)(+) species (m=1-4, 6, 8) with a high nitrogen content (n=4, 5, 8, 10-12, 20) were identified. The formation of a N(6)(-) cluster was also detected using a C(60) matrix. Under various conditions singly charged P(m)(+) (m=2-7, 9, 13), P(m)(-) (m=3-11, 13, 15, 17), N(n)(+) (n=5, 9, 10, 12, 13), and N(n)(-) (n=6, 10-15) clusters were identified in the mass spectra. Such high nitrogen content clusters (up to N(15)(-)) generated by laser desorption from a solid material are described for the first time. The stoichiometry of the P(m)N(n) clusters was determined via isotopic envelope analysis and computer modelling. The composition of the clusters with respect to the crystalline structure of α-P(3)N(5) is discussed.

Laser desorption ionization time-of-flight mass spectrometric study of binary As-Se glasses.

Binary chalcogenide As-Se glasses and their thin films are important for optics, computers, materials science and technological applications. To increase understanding of the properties of thin films fabricated by plasma deposition techniques, more information concerning the physics of plasma plume is needed. In this study the formation of clusters in plasma plume from different As-Se glasses by laser desorption ionization (LDI) or laser ablation (LA) was studied by time-of-flight mass spectrometry (TOF MS) in positive and negative ion modes. Formation of a number of As(p)Se(q) singly charged clusters As(3)Se(q)(+) (q = 1-5), AsSe(q)(-) (q = 1-3), As(2)Se(q)(-) (q = 2-4), and As(3)Se(q)(-) (q = 2-5) was found from As-Se glasses with the molar ratio As:Se in the range from 1:2 to 7:3. The stoichiometry of the As(p)Se(q) clusters was determined via isotopic envelope analysis and computer modeling. The structure of the clusters is proposed and the relationship to the structure of the parent glasses, as also suggested by Raman scattering spectra, is discussed.

Laser ablation of ternary As-S-Se glasses and time-of-flight mass spectrometric study.

Ternary chalcogenide As-S-Se glasses, important for optics, computers, material science and technological applications, are often made by pulsed laser deposition (PLD) technology but the plasma composition formed during the process is mostly unknown. Therefore, the formation of clusters in a plasma plume from different glasses was followed by laser desorption ionization (LDI) or laser ablation (LA) time-of-flight mass spectrometry (TOF MS) in positive and negative ion modes. The LA of glasses of different composition leads to the formation of a number of binary As(p)S(q), As(p)Se(r) and ternary As(p)S(q)Se(r) singly charged clusters. Series of clusters with the ratio As:chalcogen = 3:3 (As(3)S(3)(+), As(3)S(2)Se(+), As(3)SSe(2)(+)), 3:4 (As(3)S(4)(+), As(3)S(3)Se(+), As(3)S(2)Se(2)(+), As(3)SSe(3)(+), As(3)Se(4)(+)), 3:1 (As(3)S(+), As(3)Se(+)), and 3:2 (As(3)S(2)(+), As(3)SSe(+), As(3)Se(2)(+)), formed from both bulk and PLD-deposited nano-layer glass, were detected. The stoichiometry of the As(p)S(q)Se(r) clusters was determined via isotopic envelope analysis and computer modeling. The structure of the clusters is discussed.