Spike Effect in the Ion Mixing of Cr/si (100)

      Spike effect in the ion mixing of Cr/Si(100)

                 [pic 1] R. Khalfaoui, [pic 2] A. Amokrane, [pic 3] S. Tobbeche

[pic 4] Faculté des sciences, Université M. Bouguerra, Boumerdés 35000, Algeria

[pic 5] Université   des  Sciences et de la Technologie  Houari  Boumediene              

                                Faculté de Physique    Alger   Algeria    

[pic 6]Departement de Physique, Faculté des Sciences, Université El Hadj Lakhdar,

                                 Batna 05000, Algeria

Abstract :

We have investigated the mixing formation taking place at the interface of reactive metal/semiconductor [pic 7] system under ion-beam irradiation. [pic 8] was irradiated with [pic 9] and [pic 10] ions to different fluences at room temperature. The interface mixing was monitored as function of the fluence by means of Rutherford backscattering spectroscopy. The interface broadening variance was found to depend linearly on the ion fluence and suggests that the mixing is like a diffusion controlled process. The results show also that the mixing rate varies linearly with the damaged deposited energy [pic 11]. Good agreement has been obtained between the experimental observations and theoretical values predicted from local heat spike. The mixing process is only governed by the thermal local spike, no contribution was observed for the global heat spike which is expected to occur for the heavy ions as reproduced in other systems [pic 12] [1], [pic 13] [2], [pic 14] [3].

Keywords :  Mixing, Spike effect, RBS, Ion beam irradiation, Variance, Mixing rate.

Corresponding author. Tel.: +213  71 54 49 60, E-mail addresses: “stobbeche@univ-batna.dz”

And “said_tobbeche@yahoo.com “.

Département de Physique, Faculté des Sciences,

Université El Hadj Lakhdar, Batna 05000, Algeria.

I - Introduction :        

Transition metal silicides are very attractive for their great number of applications. These materials are useful for their low resistivity, high temperature stability, small lattice mismatch with [pic 15] and resistance to oxidation [4].  The ion-beam irradiation is used to produce amorphous phases or silicides in metal/semiconductor thin films at low temperature, and these phases have many potential applications as contacts and insulating layers [5].

Ion-beam induced mass transport is an important phenomenon which occurs when bombarding a metallic layer deposited on semiconductor with heavy ions which locally deposited large amount of energy and induced strong atomic diffusion which form a mixing interface and lead to chemical reactions. Ballistic and thermal spike must be considered. The ballistic model [6] which uses the ballistic properties without considering the  thermodynamic  parameters  is  valid   for  elements  with   average  atomic  number

[pic 16]< 20 [7] and for low deposited energy [pic 17] of the irradiating ion into the target. This model was completed recently by incorporating a chemically guided defect motion. On the other hand and depending on the amount of the deposited damage energy [pic 18], the thermal spike which is defined as the localized increase of very high temperature for a short duration of time, can be either local [8] or global [9]. These models consider the overlapping or nonoverlapping subcascades. Above the critical deposited energy, the overlapping subcasacades global spike predicts the mixing rate to be proportional to the square of the deposited energy [pic 19]. It has been used for high average atomic number and irradiation with heavy ions. Below the critical deposited energy the local spike process should dominate and the mixing rate is proportional to [pic 20] [10]. Recently and using  experimental results an attempt to define a range 17 < [pic 21]< 39 referred to local spike is outlined [11]. But the transition to the phase formation, the relationship to the mixing process, ballistic or thermal spike mixing, the radiation enhanced diffusion, and the individual contributions of ion-induced and thermal processes, the role of the average atomic number, the critical damage energy are not well understood yet. In this work, we investigate the mixing phase in [pic 22]system, by changing the most important parameter which is in the origin of the mixing formation. We change the deposited damage energy [pic 23] at room temperature in order to study the mixing as function of projectile parameters.