K. Clémer

Sources of optical absorption between 5.7 and 5.9eV in silica implanted with Si or O

To determine if the only source of optical absorption between 5.8 and 5.9eV is the E′ center (absorbing at 5.85eV) two separate suites of type III silica samples were implanted, one with Si and one with O. Several ion energies were used for implantation to produce layers 600 and 570nm thick in the Si case and in the O case, respectively. Concentrations of implanted ions in the layers ranged from >0.02to 0.02to<2.1at.%, with uncertainties in the concentrations less than ±5%. Optical absorption measurements were made from 2.0to6.5eV and electron spin resonance (ESR) measurements were performed at ∼20.3 and 33GHz at temperatures in the 77–100K range. Several ESR active defects were observed including the E′γ center (O vacancy), the nonbridging oxygen hole center, the peroxy radical, a possibly oxygen related center, labeled OS, and a component around g=2.0026. In the O-implantation case, by comparing the increasing optical absorption at 5.85eV with the observed decrease in the ESR E′ densities with increasing O con...

Paramagnetic point defects in (100)Si∕LaAlO3 structures: Nature and stability of the interface

The atomic nature of the interface in (100)Si∕LaAlO3 structures with nanometer-thin amorphous LaAlO3 layers of high dielectric constant (κ), deposited directly on clean (100)Si by molecular beam deposition at ∼100°C, was assessed through probing of paramagnetic point defects. On the as-grown samples K-band electron spin resonance indicated the absence of a Si∕SiO2-type interface in terms of the archetypal Si-dangling bond-type Si∕SiO2 interface defects (Pb0, Pb1). With no Pb-type defects observed, this state is found to persist during subsequent annealing (1atm N2 or 5% O2 in N2 ambient) up to the temperature Tan∼800°C, referring to a thermally stable abrupt Si∕LaAlO3 interface, quite in contrast with other high-κ metal oxide∕Si structures. However, in the range Tan∼800–860°C a Si∕SiO2-type interface starts forming as evidenced by the appearance of Pb0 defects and, with some delay in Tan, the EX center—a SiO2 associated defect, attesting to significant structural∕compositional modification. The peaking of...

Nature and stability of the (100)Si∕LaAlO3 interface probed by paramagnetic defects

Electron spin resonance analysis of (100)Si∕LaAlO3 structures reveals the absence of a Si∕SiO2-type interface in terms of archetypal Si-dangling bond-type Si∕SiO2 interface defects (Pb0,Pb1). With no Pb-type defects observed, this state is found to persist during subsequent annealing (5% O2+N2 ambient) up to Tan∼800°C, indicating a thermally stable and abrupt Si∕LaAlO3 interface. In the range Tan∼800–860°C, however, a Si∕SiO2-type interface starts forming as evidenced by the appearance of Pb0 defects and, with some delay in Tan, the EX center (a SiO2 associated defect) attesting to significant structural/compositional modification. The peaking of the defect density versus Tan curves indicates that the interlayer with SiOx nature breaks up upon annealing at Tan⩾930°C, possibly related to crystallization and silicate formation. No LaAlO3-specific point defects could be detected.

Observation of a P-associated defect in HfO2 nanolayers on (100)Si by electron spin resonance

Electron spin resonance analysis has detected a P-donor related point defect in nanometer-thick HfO2 films on (100)Si after annealing in the range of 500–900°C. Based on the principal g matrix (axial; g‖=1.9965; g⊥=1.9975) and hyperfine tensor values (A1=1425±10G, A2=1245±10G, and A3=1160±10G) inferred from consistent K- and Q-band spectrum simulations, the center is assigned to a P2-type defect—a P substituting a Hf atom—similar to P2 in silica, where the unpaired spin is strongly localized on the P atom. The annealing impact is linked to the onset of crystallization enabling substitutional positioning of the P impurities. The centers may act as detrimental charge trapping sites.