Depth distribution and migration of implanted helium in metal foils using proton backscattering

Conference · Mon Jan 01 04:00:00 EST 1973

OSTI ID:4404603

Blewer, R S

From international conference on applications of ion beams to metals; Albuquerque, New Mexico, USA (2 Oct 1973). Proton backscattering at 2.5 MeV was used to measure the mean depth and profile of implanted helium distributions as a function of implant energy, implant fluence, and post-implant anneal temperature in copper foils of varying thickness. Distributions implanted at 50, 100, and 150 keV agree with calculated ranges for helium in copper. At room temperature the shape of the distributions is Gaussian with no evidence of a supertail or of the peaks being skewed either toward the surface or the interior of the foils. Implantation of some foils was performed at two energies (highest energy first) using both equal and unequal doses. Resultant profiles were those expected from overlapping Gaussians centered at the predicted depths. Implanted helium fluences ranging from 5 x 10/sup 16/ to 3 x 10/sup 17/ He/sup +//cm/sup 2/ result in backscattering peaks for helium which increase in magnitude in the proper proportion to increasing fluence. Effect of in situ isochronal and isothermal annealing on the disposition of the implanted helium was also observed. Above 2OO deg C, the peak of the helium distribution decreases in magnitude, but no lateral spreading of the profile (as expected in Fick's Law diffusion) is observed. Moreover, the helium peak height decreases steadily for each of the isochronal temperature plateaus between 200 and 450 deg C. Isothermal annealing at 225 and 400 deg C produces almost no additional change in the magnitude of the helium peak over three anneal periods of increasing duration. Throughout annealing, the symmetric form of the Gaussian distribution is retained. There is no evidence of preferential diffusion of the implanted helium either into the undamaged depths of the foils or through the residual ion-implantation-induced damage between the helium-implanted layer and the foil surface. These observations could be explained if the helium were trapped at or near its endof- range location at room temperature and then released in proportionate fractions at progressively higher temperatures by formation and subsequent rupture of bubbles developing in the implanted layer. Evidence was obtained by scanning electron microscopy which supports this hypothesis. Simultaneous profiling of oxygen and carbon in the foils or on their surfaces is also described. (8 figures, 23 references) (auth)

• Research Organization: Sandia Labs., Albuquerque, N.Mex. (USA)
• NSA Number: NSA-29-005542
• OSTI ID: 4404603
• Report Number(s): SLA--73-5835; CONF-731028--4
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

*COPPER-- ION IMPLANTATION
*PROTONS-- BACKSCATTERING
ANNEALING
DEPTH
FOILS
HELIUM IONS
KEV RANGE 10-100
KEV RANGE 100-1000
MEV RANGE 01-10
N50240* --Metals
Ceramics
& Other Materials--Metals & Alloys--Radiation Effects
PEAKS
PROTON BEAMS
SPATIAL DISTRIBUTION