F. F. Morehead

Bio: F. F. Morehead is an academic researcher from IBM. The author has contributed to research in topics: Ion & Phenomenological model. The author has an hindex of 1, co-authored 1 publications receiving 396 citations.

A model for the formation of amorphous Si by ion bombardment

Abstract: The effective annealing of ion implantations in Si is aided by the formation of continuous amorphous layer. The amorphous layer regrows epitaxially at 500–600°C and incorporates the dopant in an electrically active, uncompensated form. A phenomenological model is proposed which, with adjustable parameters, accounts for the variation of the critical dose required to produce a continuous amorphous layer by ion bombardment with ion, target, temperature, and, with minor additional assumptions, dose rate.

Erbium implanted thin film photonic materials

Abstract: Erbium doped materials are of great interest in thin film integrated optoelectronic technology, due to their Er3+ intra-4f emission at 1.54 μm, a standard telecommunication wavelength. Er-doped dielectric thin films can be used to fabricate planar optical amplifiers or lasers that can be integrated with other devices on the same chip. Semiconductors, such as silicon, can also be doped with erbium. In this case the Er may be excited through optically or electrically generated charge carriers. Er-doped Si light-emitting diodes may find applications in Si-based optoelectronic circuits. In this article, the synthesis, characterization, and application of several different Er-doped thin film photonic materials is described. It focuses on oxide glasses (pure SiO2, phosphosilicate, borosilicate, and soda-lime glasses), ceramic thin films (Al2O3, Y2O3, LiNbO3), and amorphous and crystalline silicon, all doped with Er by ion implantation. MeV ion implantation is a technique that is ideally suited to dope these materials with Er as the ion range corresponds to the typical micron dimensions of these optical materials. The role of implantation defects, the effect of annealing, concentration dependent effects, and optical activation are discussed and compared for the various materials.

Radiation effects in crystalline ceramics for the immobilization of high-level nuclear waste and plutonium

Abstract: This review provides a comprehensive evaluation of the state-of-knowledge of radiation effects in crystalline ceramics that may be used for the immobilization of high-level nuclear waste and plutonium. The current understanding of radiation damage processes, defect generation, microstructure development, theoretical methods, and experimental methods are reviewed. Fundamental scientific and technological issues that offer opportunities for research are identified. The most important issue is the need for an understanding of the radiation-induced structural changes at the atomic, microscopic, and macroscopic levels, and the effect of these changes on the release rates of radionuclides during corrosion.

Ion implantation in semiconductors—Part II: Damage production and annealing

Abstract: Radiation damage is produced in a crystalline target whenever a moving ion transfers sufficient energy to a target atom to displace it from its lattice site. For conditions of practical importance in ion implantation, the radiation damage produced by the injected ions is severe, and the crystal must be carefully Annealed if the chemical effects of the implanted ions are to dominate the residual damage. The purpose of this paper is to review work that has been performed over the past several years in an effort to understand implantation-produced damage and its annealing characteristics, especially in silicon. The subject is developed as follows. A qualitative description of the damage produced by an implanted ion is presented in Section I, followed by a partial inventory of the basic defects that are found in ion-implanted silicon (Section II). The structure of individual damage clusters produced by both heavy and light ions is then described in Section III, where theoretical predictions are compared to a variety of experimental data. This is followed with a section on the depth distribution of defects and damage clusters (Section IV); and the paper is then concluded with a section on the annealing characteristics of implantation-produced damage (Section V). The development is organized to give primary emphasis to those facts and ideas that are essential for applications of ion implantation in the fabrication of MOS and junction devices in silicon. A future paper will review the state of the art in compound semiconductors.

Models and mechanisms of irradiation-induced amorphization in ceramics

Abstract: A number of models have been developed to describe the various amorphization processes and the effects of temperature on the kinetics of amorphization. These models are reviewed and in some cases further developed. In general, these models contain a number of parameters relating to irradiation-assisted and thermal recovery processes, which make their application to existing data sets challenging. Nonetheless, general aspects of the models yield insights into the rate-limiting processes controlling the kinetics of amorphization within a given temperature regime. Several examples are used to illustrate features of the models and to highlight differences in behavior.

The radiation-induced crystalline-to-amorphous transition in zircon

Abstract: A comprehensive understanding of radiation effects in zircon, ZrSiO4, over a broad range of time scales (0.5 h to 570 million years) has been obtained by a study of natural zircon, Pu-doped zircon, and ion-beam irradiated zircon. Radiation damage in zircon results in the simultaneous accumulation of both point defects and amorphous regions. The amorphization process is consistent with models based on the multiple overlap of particle tracks, suggesting that amorphization occurs as a result of a critical defect concentration. The amorphization dose increases with temperature in two stages (below 300 K and above 473 K) and is nearly independent of the damage source (α-decay events or heavy-ion beams) at 300 K. Recrystallization of completely amorphous zircon occurs above 1300 K and is a two-step process that involves the initial formation of pseudo-cubic ZrO2.