Materials modification with ion beams

Abstract

The incorporation of impurities into solids by bombardment with energetic ions is a non-equilibrium process which can result in intriguing near-surface property changes. This review initially examines the basic ion-solid interaction processes and outlines how such processes can lead to the modification of the composition, structure and surface topography of materials. Ion implantation has been exploited in widely diverse fields both as a powerful research tool for investigating solid state material processes and properties, and as a means of controllably modifying the electrical, physical, chemical, mechanical and optical properties of solid surfaces. These aspects receive major attention in this review which attempts to provide a balanced overview of the impact of ion implantation on solid state science and technology. In particular, special emphasis is given to implantation processes and applications in semiconductors which have received an enormous amount of attention in recent years, stimulated no doubt by the strong technological driving forces within the microelectronics industry. Ion bombardment processes and interesting property changes in metals are also discussed, and a selection of important technological applications is given. Finally, an overview of more recent investigations and applications is presented, including ion implantation into insulators and polymers, insight into crystal growth processes, adhesion of thin films to substrates, and research into ion bombardment of ices which has astrophysical significance.

Depth profile of the microhardness in helium implanted GaP

“…2 ) . Probably, this effect is due to the formation of larger agglomerates of point defects or of extended defects like voids and dislocations as they have been found in helium implanted It is interesting to note that recently reported results for the fluence dependence of the microhardness in ion implanted silicon, sapphire and some other materials (B[JRNETT, BRIGGS; BURNIWT, PAGE 1984a, b, 1985, 1986H I O K~ et al) confirm our measurements. In these investigations it has been found that the microhardness increases with the ion fluence a t low fluences, then goes through a masimum a t some critical fluence and decreases a t higher fluences.…”

Annealing of ion implanted gallium nitride

“…This is not surprising since the melting point of GaN is very high ͑2518°C͒ and the removal of crystalline defects from other compound semiconductors normally requires temperatures in excess of two thirds of the melting point ͑in K͒. 8 What is surprising is that reasonable electrical activity can be obtained in GaN with so much residual damage. In this regard, the atom location measurements are illuminating since they suggest that Te is substitutional despite the disorder.…”

“…7 In other compound semiconductors such as GaAs and InP, implantation results in extensive crystalline damage and even amorphous layers which recrystallise epitaxially during annealing up to 400°C. 8 However, in both preamorphous and amorphous cases, low temperature annealing leaves a highly defective crystal which must be annealed at considerably higher temperatures ͑up to 900°C͒ to fully remove all defects and activate dopants. [8][9][10] In GaN, recent studies [11][12][13][14] have indicated that activation of both n-and p-type dopants can be achieved by annealing up to 1100°C but results are variable and the electrical properties are far from optimum.…”

“…8 However, in both preamorphous and amorphous cases, low temperature annealing leaves a highly defective crystal which must be annealed at considerably higher temperatures ͑up to 900°C͒ to fully remove all defects and activate dopants. [8][9][10] In GaN, recent studies [11][12][13][14] have indicated that activation of both n-and p-type dopants can be achieved by annealing up to 1100°C but results are variable and the electrical properties are far from optimum. Consequently, there is an urgent need to carry out detailed studies on the structural nature of implantation damage in GaN and its removal during annealing.…”

Effect of proton irradiation on electrical properties of a-As2S3

“…An energetic ion loses its energy during its passage through material mainly by electronic energy loss (inelastic collision) and nuclear energy loss (elastic scattering). The nature of modification depends upon the electrical, thermal and structural properties of the target material, mass of projectile ion and irradiation parameter [12]. Impedance spectroscopy is a powerful technique for the study of ion transport processes [13].…”