A Combined Atomic and Molecular Probe Characterization of Aromatic Hydrocarbons via PALS and ESR: Methylbenzene

A combined study of one of the simplest aromatic hydrocarbons, i.e., methylbenzene (toluene) (TOL), via the annihilation of an ortho-positronium (o-Ps) probe via positron annihilation lifetime spectroscopy (PALS) and the rotation dynamics of nitroxide spin probe 2,2,6,6-tetramethyl-piperidinyl-1-oxy (TEMPO) using electron spin resonance (ESR) over a wide temperature range, 10–300 K, is reported. The o-Ps lifetime, τ3, and the relative o-Ps intensity, I3, as a function of temperature exhibit changes defining several characteristic PALS temperatures in the slowly and rapidly cooled samples. Similarly, the spectral parameter of TEMPO mobility in TOL, 2Azz‘, and its correlation time, τc, reveal several effects at a set of the characteristic ESR temperatures, which were determined and compared with the PALS results. Finally, the physical origins of the changes in free volume expansion and spin probe mobility are revealed. They are reflected in a series of the mutual coincidences between the characteristic PALS and ESR temperatures and appropriate complementary thermodynamic and dynamic techniques.

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Electron Spin Resonance Characterization of Defects at Interfaces in Stacks of Ultrathin High-κ Dielectric Layers on Silicon

MRS Proceedings ◽

10.1557/proc-786-e1.4 ◽

2003 ◽

Vol 786 ◽

Author(s):

A. L. Stesmans ◽

V.V. Afanas'ev

Keyword(s):

Electron Spin Resonance ◽

Electron Spin ◽

Chemical Vapor ◽

Deposition Process ◽

Dielectric Layers ◽

Growth Standard ◽

Spin Resonance ◽

Dielectric Interfaces ◽

Standard Quality

ABSTRACTElectron spin resonance (ESR) analysis of (100)Si/SiOx/ZrO2, (100)Si/Al2O3 and Si/HfO2 structures with nm-thin dielectric layers deposited by different chemical vapor deposition procedures reveals, after hydrogen detachment, the presence of the trivalent Si dangling-bond-type centers Pb0, Pb1 as prominent defects in all entities. This Pb0, Pb1 fingerprint, generally unique for the thermal (100)Si/SiO2 interface, indicates that the as-deposited (100)Si/metal oxides interface is basically Si/SiO2-like. Though sensitive to the deposition process, the Pb0 density is found to be substantially larger than in standard (100)Si/SiO2. As probed by the Pb- type center properties, the Si/dielectric interfaces of all structures are under enhanced (unrelaxed) stress, typical for low temperature Si/SiO2 growth. Standard quality thermal Si/SiO2 properties in terms of Pb signature may be approached by appropriate annealing (≥ 650°C) in vacuum in the case of (100)Si/SiOx/ZrO2. Yet, O2 ambient appears required for Si/Al2O3 and Si/HfO2. It appears that Si/high-κ metal oxide structures with device grade quality interfaces can be realized with sub-nm thin SiOx interlayers. The density of fast interface states closely matches the Pb0 density variations, suggesting the center as the dominant fast interface trap. They may be efficiently passivated in H2 at 400 °C.

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