Accumulation of structural defects in silicon irradiated with PF n + cluster ions with medium energies

  • PDF / 191,681 Bytes
  • 6 Pages / 612 x 792 pts (letter) Page_size
  • 65 Downloads / 190 Views

DOWNLOAD

REPORT


IC STRUCTURE AND NONELECTRONIC PROPERTIES OF SEMICONDUCTORS

Accumulation of Structural Defects in Silicon Irradiated with P F+n Cluster Ions with Medium Energies A. Yu. Azarova^ and A. I. Titovb aElectron–Optronic

State Unitary Research and Production Company, St. Petersburg, 194223 Russia ^e-mail: [email protected] bSt. Petersburg State Polytechnical University, St. Petersburg, 195251 Russia Submitted April 27, 2006; accepted for publication May 10, 2006

Abstract—The method of Rutherford backscattering spectrometry in combination with channeling is used to study the accumulation of structural defects in silicon at room temperature as a result of irradiation with P+ and + F+ atomic ions and also with cluster P F n ions (n = 1, …, 4) with the energy of 2.1 keV/amu and with identical generation rate of primary defects. The conditions for correct comparison of the results of bombardment with atomic and cluster ions composed of atoms of various types are suggested. It is found that the characteristics of + accumulation of structural defects in silicon in the case of bombardment with P F n cluster ions differ widely from those under irradiation with both atomic ions that are involved in the cluster ion (P+ and F+) and with + atomic heavy ions that have atomic mass close to that of the mass of a P F n cluster. It is shown that, with irradiation conditions being the same, cluster ions produce much more radiation defects in the surface region than do atomic ions; i.e., a molecular effect is observed. Plausible mechanisms of this phenomenon are considered. PACS numbers: 61.72.Tt, 61.80.Lj, 61.80.-x, 68.55.Ln DOI: 10.1134/S1063782607010022

1. INTRODUCTION

alent conditions can appear near the surface of a solid. As a result, the efficiency per incident ion of many processes accompanying the implantation of accelerated ions (formation of structural defects, sputtering, ion mixing, electron and ion emission, and so on) can be different under irradiation with atomic and cluster ions under equivalent conditions [1–13]. This phenomenon is known as the molecular effect (ME); its efficiency in the case of production of structural defects (γ) is typically expressed as the ratio between the concentrations of stable defects per incident atom in the cases of irradiation with cluster and atomic ions. Typically, in the case of irradiation of silicon with biatomic ions, the + efficiency does not exceed γ = 2; however, if C 60 cluster ions are implanted, the value of γ is in excess of 100 [16]. Nevertheless, the value of ME efficiency obtained in [16] should be refined, since the condition for the correct choice of the ion-current density in the cases of irradiation of Si with atomic and cluster ions was not satisfied in [16] (see below for more details).

In recent years, increased interest has been attracted to the processes that occur in a material irradiated with molecular and cluster ions since bombardment with these ions opens new possibilities for modification and analysis of the properties of surface layers [1–13]. In particula

Data Loading...