Fabrice Gourbilleau

Active emitters based on nanostructured Si

The present paper deals with the use of Si nanoclusters as efficient sensitisers for Er and Nd rare earth ions or as active emitters in Si/SiO2 Fabry-Perot microcavities. The films have been fabricated using the reactive magnetron sputtering of a silica target. The energy transfer efficiency from Si-nc towards Er ions has been studied as a function of the fabrication parameters (hydrogen rate, annealing temperature) through time resolved PL intensity measurements on Er-doped silicon-rich silica layers. A multilayer approach has been developed to determine the critical parameters such as the optimum Si-nc size and the characteristic interaction distance Si-nc-Er ions which govern the transfer Si-nc-Er. Thus we have found an optimum size of 4 nm for the Si nanocluster and a maximum spacing of 0.4 nm between the Si-nc sensitisers and the Er3+ ions. First results on the efficient sensitising effect of Si nanocluster towards Nd3+ ions are also reported. Concerning the optical planar Si/SiO2 microcavities, spectral, spatial and temporal photoluminescence behaviour of the Si/SiO2 multilayers confined inside the resonator are studied. The comparison with a reference sample evidences the effect of the distributed Bragg reflectors structure on the intensity enhancement and the directional characteristic of the emission.

Silicon Nanoclusters Embedded into Oxide Host for Non-Volatile Memory Applications

Non-volatile memory structures with embedded silicon nanoclusters were fabricated by RF magnetron sputtering approach. The capacitance-voltage characteristics of classical SiO2/Si-ncs-SiO2/SiO2 and HfO2/Si-ncs-SiO2/SiO2 structures have been compared. The specific deposition conditions and annealing treatment allowed a large memory window of about 6.8 V at a sweeping voltage of ± 6 V to be achieved. It was observed that the similar memory capacitance can be obtained for classical SiO2/Si-ncs-SiO2/SiO2 structures using multilayer charge storage node. The analysis of microstructural properties of the samples revealed that an annealing at 1000-1100°C results in the formation of crystallized silicon clusters, while the crystallization of HfO2 occurred with a tetragonal phase. It was also revealed that an annealing treatment at 950°C, at which amorphous Si clusters are formed, allowed a highest memory window to be obtained. This result indicates the benefit of low thermal budget treatment for low operating voltage non-volatile memory devices.

Effect of rapid thermal annealing on Nd-SiO x thin film properties

The series of Nd3+-doped Si-rich SiO2 thin films with different excess Si content were deposited by magnetron co-sputtering of three different (SiO2, Si and Nd2O3) targets under a plasma of pure argon at 500 °C. The Si excess content in the samples was monitored via a power applied on Si cathode. The films were submitted to the rapid thermal annealing (RTA) at 900, 1000 and 1100 °C, respectively. It was observed a phase separation and a formation of Si nanoclusters embedded in oxide host. The Si excess, remaining after a RTA-1100 °C annealing, was found to be negligible, confirmed nearly complete phase separation. The Nd3+ photoluminescence (PL) property was explored as a function of Si excess and/or annealing temperature. The most efficient Nd3+ PL emission was found for the samples with about 4.7% of Si excess. These optimal samples, submitted to RTA-900 °C-1 min treatment and conventional annealing at 900°C for 1 h in nitrogen flow, demonstrated comparable Nd3+ PL intensities. This offers future application of RTA treatment to achieve an efficient emission from the materials doped with rare-earth ions.The series of Nd 3+-doped Si-rich SiO 2 thin films with different excess Si content were deposited by magnetron co-sputtering of three different (SiO 2 , Si and Nd 2 O 3) targets under a plasma of pure argon at 500 oC. The Si excess content in the samples was monitored via a power applied on Si cathode. The films were submitted to the rapid thermal annealing (RTA) at 900, 1000 and 1100 oC, respectively. It was observed a phase separation and a formation of Si nanoclusters embedded in oxide host. The Si excess, remaining after a RTA-1100 oC annealing, was found to be negligible, confirmed nearly complete phase separation. The Nd 3+ photoluminescence (PL) property was explored as a function of Si excess and/or annealing temperature. The most efficient Nd 3+ PL emission was found for the samples with about 4.7% of Si excess. These optimal samples, submitted to RTA-900 oC-1 min treatment and conventional annealing at 900°C for 1 h in nitrogen flow, demonstrated comparable Nd 3+ PL intensities. This offers future application of RTA treatment to achieve an efficient emission from the materials doped with rare-earth ions.

Preface to Symposium E: Nanoscaled Si, Ge based Materials.

This special volume of Nanoscale Research Letters features selected papers presented at the Symposium E : Nanoscaled Si, Ge based Materials of the EMRS Fall meeting, held in Warsaw, Poland from September 13th-16, 2010.

Stable HfO2 based Layers Fabricated by RF Magnetron Sputtering

Structural and composition properties of HfO2-based layers fabricated by RF magnetron sputtering were studied by means of X-ray diffraction and transmission electron microscopy, Energy dispersive spectroscopy and ATR-FTIR techniques versus the deposition parameters and post-deposition annealing treatment. It was observed that the temperature at which amorphous-crystalline transformation of pure HfO2 layers occurs depends on deposition conditions. It was found that silicon incorporation in HfO2 matrix plays main role in the stability of the layers and allows to increase the temperature of layer crystallization up to 900-1100 °C.