XTEM
observations revealing high diffusivity and Ge segregation in
UV
laser pulse annealed
S
i
G
e
O
and
G
e
T
i
O
amorphous films
Authors: Serban Teodorescu Valentin , Teodorescu Valentin Serban , Maraloiu Adriaan Valentin , Kuncser Andrei , Ghica Corneliu , Ciurea Magdalena Lidia , Lepadatu Ana‐Maria , Stavarache Ionel , Scarisoreanu Doinel Nicolae , Blanchin Marie‐Genevieve , Dinescu Ana‐Maria 
Published: December 2016

XTEM observations revealing high diffusivity and Ge segregation in UV laser pulse annealed SiGeO and GeTiO amorphous films

V.S. Teodorescu
1
, A.V. Maraloiu
1
, A. Kuncser
1
, C. Ghica
1
, M.L. Ciurea
1
, A.M. Lepadatu
1
,

I. Stavarache
1
, D.N. Scarisoreanu
2
, M. Dinescu
2
, M‐G. Blanchin
3

1

National Institute of Materials Physics, 077125, Bucharest‐Magurele, Romania

2

National Institute of Lasers Plasma and Radiation Physics, 077125 Bucharest‐Magurele, Romania

3

ILM‐ Université Claude Bernard Lyon1, 69622 Villeurbanne Cedex, France

Ge nanoparticles embedded in dielectric oxide matrix are very interesting for application in memory devices. Amorphous SiGeO and GeTiO films with different Ge/oxide ratio where produced by magnetron sputtering deposition on Si wafers. In these systems, the Ge nanoparticles are formed during RTA annealing by segregation of the Ge atoms via a nucleation and growth processes. The Ge nanoparticles can remain in amorphous state or become crystallized. The SiO
2
matrix remains amorphous after annealing, but the TiO
2
matrix crystallize in the same time with the Ge nanocrystals formation in the case of RTA annealing or remain amorphous in the case of laser pulse annealing [1]. The SiGeO and the GeTiO oxide films were laser pulse irradiated, using the forth harmonics radiation of the Nd‐YAG laser (l = 266 nm) and a low laser pulse fluences between 15 and 100 mJ/cm
2
. These fluence values are less than the melting threshold of the amorphous oxide films.

The nanoscale films structure investigation was performed with the JEM ARM200F electron microscope using specimens prepared by cross section method (XTEM). The structural modifications induced by the laser pulse irradiation are present under the film surface in a depth of about 60 to 80 nm, which is more than the expected absorption depth of the laser radiation. The XTEM structural study is the only method for the study of the structural modifications induced by the laser pulse irradiation in a nanometric layer under the film surface. Figure 1 shows the Ge segregation under surface of the irradiated GeTiO amorphous film. The Ge nanoparticle and the titanium oxide matrix remain amorphous after the laser annealing. Figure 2 shows a similar situation in the case of the SiGeO amorphous film. In this case, the estimated temperature of the film surface is close to the Ge melting point in a lapse of time of the order of magnitude of 10ns.
In all cases, the oxide matrix remains in solid phase during the laser pulse action. Formation of the Ge nanoparticles during laser pulse action shows the presence of a very high diffusivity of the Ge atoms in the laser pulse field, similar to the diffusivity taking place in the liquid state.
This work was supported by PNII‐ ID –project number 289/2011.