On the stabilization of ion sputtered surfaces

The classical theory of ion beam sputtering predicts the instability of a flat surface to uniform ion irradiation at any incidence angle. We relax the assumption of the classical theory that the average surface erosion rate is determined by a Gaussian response function representing the effect of the collision cascade and consider the surface dynamics for other physically-motivated response functions. We show that although instability of flat surfaces at any beam angle results from all Gaussian and a wide class of non-Gaussian erosive response functions, there exist classes of modifications to the response that can have a dramatic effect. In contrast to the classical theory, these types of response render the flat surface linearly stable, while imperceptibly modifying the predicted sputter yield vs. incidence angle. We discuss the possibility that such corrections underlie recent reports of a ``window of stability'' of ion-bombarded surfaces at a range of beam angles for certain ion and surface types, and describe some characteristic aspects of pattern evolution near the transition from unstable to stable dynamics. We point out that careful analysis of the transition regime may provide valuable tests for the consistency of any theory of pattern formation on ion sputtered surfaces

Development of Knife-Edge Ridges on Ion-Bombarded Surfaces

We demonstrate in both laboratory and numerical experiments that ion bombardment of a modestly sloped surface can create knife-edge like ridges with extremely high slopes. Small pre-fabricated pits expand under ion bombardment, and the collision of two such pits creates knife-edge ridges. Both laboratory and numerical experiments show that the pit propagation speed and the precise shape of the knife edge ridges are universal, independent of initial conditions, as has been predicted theoretically. These observations suggest a novel method of fabrication in which a surface is pre-patterned so that it dynamically evolves to a desired target pattern made of knife-edge ridges.Comment: 5 pages, 4 figure

Pengembangan Bahan Ajar IPS Model Shared Kelas VIII

This study aims to develop teaching materials of social studies use model Shared class VIII SMP with the theme "Environment and Community Economic Activities" is feasible and interesting, and foster self-reliance in students in learning based on the test of material and media expert, And students viewed from the aspects of material / content, language, presentation, and graphic. The research method used is Research and Development (R & D) Borg and Gall. Module development design and procedures follow the development steps of Hilda Taba. Technique of data collection is done by using interview technique, observation, and questionnaire. The data analysis technique uses quantitative descriptive data analysis expressed in the five scale scores. The results of the module feasibility test by the material expert obtained the assessment with the category of "good", the media experts obtained the category of "very good", teacher and students assessment get the category "good". Based on feasibility tests by experts, teachers and students indicates that the IPS module model shared of VIII class is very systematic, consistent, interesting, highly appropriate, and very appropriate, for use in learning activities.Penelitian ini bertujuan untuk mengembangkan bahan ajar IPS model Shared kelas VIII SMP dengan tema “Lingkungan dan Kegiatan Ekonomi Masyarakat” yang layak, menarik, menumbuhkan kemandirian pada diri siswa dalam pembelajaran berdasarkan hasil uji ahli materi dan ahli media, penilaian guru dan siswa. Metode penelitian yang digunakan adalah metode Research and Development (R&D) Borg and Gall. Desain dan prosedur pengembangan modul mengikuti model pengembangan Hilda Taba.Teknik pengumpulan data dilakukan dengan menggunakan teknik wawancara, observasi, dan angket.Teknik analisis data menggunakan analisis data deskriptif kuantitatif yang dinyatakan dalam skor skala lima. Hasil uji kelayakan modul oleh ahli materi memperoleh kategori “baik”, ahli media memperoleh kategori “sangat baik”, guru dan siswa memperoleh kategori “baik”. Berdasarkan uji kelayakan oleh ahli, guru, dan siswa menunjukkan modul IPS model shared kelas VIII sangat sistematis, konsisten, menarik, sesuai, tepat, untuk digunakan dalam kegiatan pembelajaran