Structural modifications of low-energy heavy-ion irradiated germanium

Journal Article · Thu Sep 01 00:00:00 EDT 2011 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.84.104108· OSTI ID:21596860

Steinbach, T; Wernecke, J; Wesch, W ^[1]; Kluth, P; Ridgway, M C ^[2]

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1. Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)
2. Australian National University, Research School of Physics and Engineering, Canberra (Australia)

Heavy-ion irradiation of crystalline germanium (c-Ge) results in the formation of a homogeneous amorphous germanium (a-Ge) layer at the surface. This a-Ge layer undergoes structural modification such as a strong volume expansion accompanied by drastic surface blackening with further ion irradiation. In the present paper we investigate the mechanism of this ion-induced structural modification in a-Ge basically for the irradiation with I ions (3 and 9 MeV) at room and low temperature as a function of ion fluence for the ion incidence angles of {Theta}=7 deg. and {Theta}=45 deg. For comparison, Ag- and Au-ion irradiations were performed at room temperature as a function of the ion fluence. At fluences two orders of magnitude above the amorphization threshold, morphological changes were observed for all irradiation conditions used. Over a wide range of ion fluences we demonstrate that the volume expansion is caused by the formation of voids at the surface and in the depth of the projected ion range. At high ion fluences the amorphous layer transforms into a porous structure as established by cross section and plan view electron microscopy investigations. However, the formation depth of the surface and buried voids as well as the shape and the dimension of the final porous structure depend on the ion fluence, ion species, and irradiation temperature and will be discussed in detail. The rate of the volume expansion (i.e., porous layer formation) depends linearly on the value of {epsilon}{sub n}. This clearly demonstrates that the structural changes are determined solely by the nuclear energy deposited within the amorphous phase. In addition, at high ion fluences all perpendicular ion irradiations lead to a formation of a microstructure at the surface, whereas for nonperpendicular ion irradiations a nonsaturating irreversible plastic deformation (ion hammering) without a microstructure formation is observed. For the irradiation with ion energies of several MeV, the effect of plastic deformation shows a linear dependence on the ion fluence. Based on these results, we provide an explanation for the differences in surface morphology observed for different angles of incidence of the ion beam will be discussed in detail.

• OSTI ID: 21596860
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 84, Issue 10; Other Information: DOI: 10.1103/PhysRevB.84.104108; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
AMORPHOUS STATE
COMPARATIVE EVALUATIONS
CROSS SECTIONS
CRYSTAL DEFECTS
ELECTRON MICROSCOPY
GERMANIUM
GOLD IONS
HEAVY IONS
INCIDENCE ANGLE
IODINE IONS
ION BEAMS
IRRADIATION
LAYERS
MEV RANGE 01-10
MODIFICATIONS
NUCLEAR ENERGY
PHYSICAL RADIATION EFFECTS
PLASTICITY
POROUS MATERIALS
SURFACES
BEAMS
CHARGED PARTICLES
CRYSTAL STRUCTURE
ELEMENTS
ENERGY
ENERGY RANGE
EVALUATION
IONS
MATERIALS
MECHANICAL PROPERTIES
METALS
MEV RANGE
MICROSCOPY
RADIATION EFFECTS