Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The surface and interface sensitive nonlinear optical technique of second-harmonic generation ͑SHG͒ is a very useful diagnostic in studying surface and interface properties in thin film systems and can provide relevant information during thin film processing. An important aspect when applying SHG is the interpretation of the SHG response. In order to utilize the full potential of SHG during materials processing it is necessary to have a good understanding of both the macroscopic and the microscopic origin of the SHG response, particularly in thin film or multilayer systems where the propagation of radiation is another important aspect that should be considered carefully. A brief theoretical overview on the origin of the SHG response and a description of the propagation of radiation will be given. Furthermore, several methods will be discussed that might reveal the possible macroscopic and microscopic origins of the SHG response in thin film systems. The different approaches will be illustrated by examples of real-time and spectroscopic SHG experiments with thin film systems relevant in Si etching and deposition environments, such as ͑1͒ hydrogenated amorphous Si films deposited by hot-wire chemical vapor deposition on both Si͑100͒ and fused silica substrates, ͑2͒ amorphous Si generated by low-energy Ar + -ion bombardment of H terminated Si͑100͒, and ͑3͒ Al 2 O 3 films deposited by plasma-assisted atomic layer deposition on H terminated Si͑100͒.

The structure of an H(2)O monolayer bound to atomically smooth hydroxylated amorphous silica is probed under ambient conditions by near-infrared evanescent-wave cavity ring-down absorption spectroscopy. Employing a miniature monolithic optical resonator, we find sharp (approximately 10 cm(-1)) and polarized (>10:1) vibration-combination bands for surface OH and adsorbed H(2)O, which reveal ordered species in distinct local environments. Indicating first-monolayer uniqueness, the absorption bands for adsorbed H(2)O show intensity saturation and line narrowing with completion of one monolayer. Formation of the ordered H(2)O monolayer likely arises from H bonding to a quasicrystalline surface OH network.

Circular dichroism in second harmonic generation (SHG) is often related to molecules and materials with chiral structures. In this letter, we report circular dichroism in SHG from anisotropic achiral oxidized Si (001) at room temperature. The dichroism value depends on the azimuthal angles of the crystal axes. Due to the simple nonlinear susceptibility elements involved, we were able to attribute the dichroism in SHG to interference between particular terms of the bulk electric quadrupole and surface dipole contributions. The presence of a phase shift between the bulk and surface SHG is required to observe circular dichroism.

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