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Internal photoemission of electrons from 4- and 2-monolayer thick MoS 2 films prepared by sulphurization of metallic Mo on top of SiO 2 or HfO 2 /SiO 2 insulating stacks is detected. This enables determination of the energy position of the MoS 2 valence band which is found to be at 4.1–4.2 eV below the SiO 2 conduction band. At the interface with HfO 2 , a barrier height of 3.7 eV is found, corresponding to an increase of the electron affinity of MoS 2 by ≈0.5 eV as compared to the SiO 2 case. This suggests the presence of interface charges (or dipoles) in the interfacial HfO 2 layer. [ABSTRACT FROM AUTHOR]

Abstract: Electron spin resonance study of low-κ insulating layers reveals that from a defect perspective these materials resemble oxygen-rich silicon dioxide matrices. The layers fabricated using porogen technology also contain a considerable amount of residual carbon in the form of clusters. Furthermore, ion sputtering damage generates additional defects provisionally identified as dangling bonds in the silicon oxycarbide clusters. The density of these defects is found to increase with increasing porosity of the low-κ insulator. Nevertheless, a lower defect density may be attained if using a porogen-free self-assembly technology. [Copyright &y& Elsevier]

Examines the defects in silicon dioxide following irradiation with energetic photons. Role of electron trapping defects on oxidation conduction bands; Impact of hydrogen (H)-complexed oxygen vacancy in silicon dioxide on electron behavior; Correlation between the electrical properties of H-complexed vacancies and stress-induced traps in thin oxides.

Investigates the density of silicon (Si) islands trapped in buried silicon dioxide layers. Implantation of oxygen into (001)Si substrates; Presence of phase remnants with reduced harmonic frequency etch rate; Result of the enhanced internal pressure inside the Si crystal.

Highlights: [•] The thermal stability of the SiGe/SiO2 interfaces of (100)Si/SiO2/Ge0.75S0.25/SiO2 structures has been studied. [•] The SiGe/SiO2 interface is found to be vulnerable to degradation by post growth thermal treatment in vacuum and hydrogen at temperatures ≳440°C. [•] No significant difference was found in thermal degradation of the SiGe/SiO2 interface between vacuum and H2 ambient. [•] A full review was made by comparing data to previous studies done on (100) and (111)Si/SiO2 interfaces. [•] Unlike Si/SiO2, H2 has no catalytic effect on thermal degradation of the SiGe/SiO2 interface. [•] The temperature of technological passivation treatment of the SiGe/SiO2 interface should not exceed 440°C. [ABSTRACT FROM AUTHOR]

A Q-band electron spin resonance (ESR) study is reported of E′ type point defects observed in ∼7nm-sized fumed silica nanoparticles following 10-eV irradiation to photodissociate H from passivated defects. In a comparative study with bulk silica (suprasil), the E′ center is used as an atomic probe to get more in depth information on the network structure of the nm-sized particles. The nanoparticles were brought into contact with ‘bulk’ Si/SiO2 entities at an elevated temperature in vacuum (Tan=1105°C), i.e., the presence of an Si/SiO2 interface. As a result of this post manufacture treatment, the E′ density increased drastically (>order of magnitude), enabling us to resolve hyperfine (hf) structure of the E′ centers located in the core region of the nanoparticles. Two doublet structures are observed, one each assigned to O2Si–H entities and the primary 29Si hf structure of the E′ centers. Analysis of these hf spectra reveals interesting information on the network structure of the core region of the nanoparticles: (1) Fumed silica is found to contain relatively less hydrogen than suprasil. (2) An increased 29Si hf splitting (439±2G) is observed compared to bulk silica (418±2G), indicating that the E′ centers located in the core of the nanoparticles exhibit on average a slightly more pyramidal defect structure, and moreover, providing evidence that the fumed silica particles are densified compared to standard bulk silica, possibly originating from the presence of more low-membered rings (n<5) in the nm-sized silica network. [Copyright &y& Elsevier]

Abstract: Results are presented of an electron spin resonance (ESR) characterization of E′ type defects observed in fumed ∼7-nm sized silica nanoparticles. This is accomplished through K- and Q-band ESR following 10-eV irradiation used to photo-dissociate H from passivated defects. The defect analysis provides access to the structure of the nanoscale on atomic level, herewith adding an extra dimension for analysis. To assess specific physico-chemical structural aspects of the particles, the E′ centers have been monitored as a function of thermal treatment in vacuum in the range 850–1115 °C, revealing the presence of two systems of E′ centers. The first one exhibits ESR parameters very similar to those of the familiar E′γ center encountered in bulk fused silica, while the second bath exhibits an altered zero crossing g value and line shape, attributed to variations in local structure. While the first E′ system most likely resides in the core regions of the nanoparticles, the second system may mainly be confined to the outer SiO2 layers exposing a structurally different, possibly more strained nature than macroscopic glassy SiO2. Probing of fundamental point defects in nanometer-sized silica particles thus reveals structural variations and non-uniformity, indicative of a structure different from bulk material. [Copyright &y& Elsevier]

Abstract: A low-temperature electron spin resonance (ESR) study has been carried out on thermal (110)Si/SiO2 as a function of oxidation temperature T ox with the intend to evaluate on atomic level the interface nature in terms of occurring inherent point defects which are at the origin of technologically detrimental traps. This reveals a remarkably high density of Pb-type interface centers (interfacial Si dangling bonds), which variant, based on coinciding ESR parameters, is typified as Pb0 (110), close to Pb0 (100) at the (100)Si/SiO2 interface. Starting at 7.5×1012 cm−2, from T ox ≈700°C onward, the density [Pb0 (110)] gradually decreases by about 50% for T ox →1100°C – a result of global structural relaxation of the top SiO2 layer as exposed by several ESR parameters. In terms of Pb(0) centers, the (110) face is found to be the worst of all three low-index Si interfaces, i.e., [Pb0 (100)]<[Pb (111)]<[Pb0 (110)], over the range T ox <∼900°C. For T ox ⩾900°C, the (110)Si face does slightly improve over the (111)Si one, herewith underlining the importance of T ox not only for such comparative defect studies but also for interface optimization. [Copyright &y& Elsevier]

Highlights: [•] Hole-trapping on Si–H bond facilitates creation of neutral centres. [•] Proton released from Si–H bond has a dramatic effect on the defect’s levels. [•] A proton nearby the neutral defect can facilitate electron transfer from Si substrate onto defect. [Copyright &y& Elsevier]