J.Y. Feng

Improvement of the thermal stability of NiSi films by using a thin Pt interlayer

The effect of a thin interlayer of Pt on the stability of NiSi films on Si(111) substrates has been investigated. Both x-ray diffraction (XRD) data and sheet resistance measurements show a remarkable improvement in the thermal stability of NiSi due to the Pt interlayer. Detailed study on the XRD data shows PtSi and NiSi form a solid solution following a Vegard’s law. It was found in Ni/Pt/Si samples that a transition in NiSi texture from (200)NiSi‖(111)Si to (002)NiSi‖(111)Si took place before the nucleation of NiSi2, which may contribute to the enhanced stability of NiSi films.

Photoluminescence origins of the porous silicon nanowire arrays

We investigate the photoluminescence (PL) behavior of the porous silicon nanowire (PSiNW) arrays synthesized via metal-assisted electroless etching method on the n-Si (100) substrate. Two PL bands with different origins dependent on the post-chemical treatments were detected. The red emission band, the peak position of which is insensitive to temperature and excitation source, is considered to originate from the excitons localized at the interface between the Si nanostructure and the oxide layer. An anomalous blue shift of the near-infrared PL band was observed when the temperature increased from 80 to 290 K. The maximum intensity appears around 160 K and the emission energy is strongly dependent on the excitation energy and power. The triplet-singlet state transition is introduced to explain the PL behavior for this emission band. The absorption spectra are also induced to confirm the PL origins.

Improved photoluminescence of silicon nanocrystals in silicon nitride prepared by ammonia sputtering

In the present work we investigated the photoluminescence property of silicon nanocrystals in silicon nitride prepared by ammonia sputtering. Silicon nanocrystals were demonstrated to form even after thermal annealing at 700 °C. Compared with the control sample using N(2) as the reactive gas, the luminescence intensity of silicon nanocrystals in silicon nitride prepared by NH(3) sputtering was greatly increased. The improvement in photoluminescence was attributed to the introduction of hydrogen-related bonds, which could well passivate the nonradiative defects existing at the interface between silicon nanocrystals and the silicon nitride matrix.

Comparison of the thermal stability of NiSi films in Ni/Pt/(111)Si and Ni/Pt/(100)Si systems

The thermal stability of NiSi films in Ni/Pt/(111)Si and Ni/Pt/(100)Si bilayered systems was investigated. In the Ni/Pt/(111)Si system, the NiSi films formed at 640 °C have an epitaxial relationship of (100)NiSi∥(111)Si and [010]NiSi∥[011]Si with the substrates. On the other hand, those formed on (100)Si substrates were polycrystalline although the experimental parameters are the same as those in Ni/Pt/(111)Si samples. In both cases, NiSi and PtSi formed a solid solution Ni1−xPtxSi following Vegard’s law. While the thermal stability of NiSi films is improved in both cases compared with the Ni/Si system, the thermal stability of the textured NiSi films formed on (111)Si substrates is higher than their polycrystalline counterparts formed on (100)Si substrates. This is attributed to the reduced interfacial energy and consequently increased activation energy for the nucleation of NiSi2 due to the formation of textured NiSi films on (111)Si substrates. At 900 °C, the Ni(Pt)Si film formed in Ni/Pt/(100)Si system decomposed into separate phases of NiSi and PtSi with noticeable lattice deformation. Differences between the texture evolution of NiSi films in Ni/Pt/Si and Ni(Pt) alloy/Si systems were also reported and explained from both kinetic and thermodynamic aspects.The thermal stability of NiSi films in Ni/Pt/(111)Si and Ni/Pt/(100)Si bilayered systems was investigated. In the Ni/Pt/(111)Si system, the NiSi films formed at 640 °C have an epitaxial relationship of (100)NiSi∥(111)Si and [010]NiSi∥[011]Si with the substrates. On the other hand, those formed on (100)Si substrates were polycrystalline although the experimental parameters are the same as those in Ni/Pt/(111)Si samples. In both cases, NiSi and PtSi formed a solid solution Ni1−xPtxSi following Vegard’s law. While the thermal stability of NiSi films is improved in both cases compared with the Ni/Si system, the thermal stability of the textured NiSi films formed on (111)Si substrates is higher than their polycrystalline counterparts formed on (100)Si substrates. This is attributed to the reduced interfacial energy and consequently increased activation energy for the nucleation of NiSi2 due to the formation of textured NiSi films on (111)Si substrates. At 900 °C, the Ni(Pt)Si film formed in Ni/Pt/(100)Si sys...

Film thickness dependence of the NiSi-to-NiSi2 transition temperature in the Ni/Pt/Si(100) system

The effect of film thickness on the NiSi-to-NiSi2 transition temperature in the Ni/Pt/Si(100) system has been studied. Three sets of Ni/Pt/Si(100) bilayered samples with the same Ni:Pt ratios but with different film thicknesses were annealed by rapid thermal annealing at 750–900 °C. Both the x-ray diffraction analysis and the sheet resistance measurement show that the thermal stability of Ni(Pt)Si films improves with a decrease in film thickness. This property of Ni(Pt)Si films reveals the good potential for its applications in ultrashallow junctions. The experimental results are explained in terms of classical nucleation theory.

Effect of a Ge interlayer on the high-temperature behavior of NiSi films

The effect of a thin Ge interlayer on the formation of Ni silicides on (100)Si substrates has been investigated. X-ray diffraction shows a remarkable increase of the nucleation temperature of NiSi2 in the presence of the Ge interlayer. Four-probe measurements show that the sheet resistance of silicide formed in Ni∕Ge∕Si system remains stable up to 850 °C, while the sheet resistance of silicide formed in Ni∕Si system presents a significant increase at 750 °C. Scanning electron microscopy indicates that island formation is not observed in the NiSi film grown on Ge∕Si substrate annealing at 800 °C. The classical nucleation theory is employed to explain the increased temperature of the nucleation of NiSi2 in the Ni∕Ge-Si system.

Investigations on structural properties of carbon nitride films synthesized by reactive ionized cluster beam deposition

Abstract Carbon nitride thin films have been prepared by reactive ionized cluster beam (RICB) technique, using low molecular weight polyethylene as evaporation material and NH3, N2 as reactive gas. Rutherford backscattering measurements show that the composition ratio, N C , as high as 0.67, can be obtained. Transmission electron microscopy investigations suggest that the films contain the crystalline β-C3N4 phase. Infrared absorption measurements indicate that chemical bonds are formed between carbon and nitrogen atoms. The results also show that the structure of the films varied mainly with the RICB parameters: ionization current and acceleration voltage.

Growth of CN films by reactive ionized cluster beam deposition

Abstract Growth of CN films on Si(111) is realized by reactive ionized cluster beam deposition (RICBD). X-ray diffraction (XRD) shows the occurrence of new CN compound which is supposed to be β-C3N4 in the films. Reflection high-energy electron diffraction (RHEED) demonstrated the coexistence of amorphous and crystalline CN compounds. Single bonded CN and triple bonded CN were identified by infrared absorption spectra. X-ray photoelectron spectra show 20% N incorporated into the films and certify the bonding energy of C 1s and N 1s. Two peaks are observed in C 1s and N 1s core level spectra. The Knoop hardness of CN films is related to accelerating voltage and ionizing current, and reaches 6200 kgf/mm2.

Simulation study on Si and Ge film growth by cluster deposition

Abstract Si and Ge thin film growth from cluster beams has been investigated with molecular-dynamics simulations utilizing the Stillinger–Weber (SW) two- and three-body interaction potentials. The spreading of cluster atoms and the structure of grown films have been studied as a function of incident cluster velocity. We found that higher surface diffusion and spreading of the deposited clusters, which were achieved with a moderate cluster velocity, are necessary for the epitaxial film. However, a very high cluster velocity leads to the damage of the substrate and the growing films. The substrate temperature also plays an important role in the growth of the films.

Carbon nitride films synthesized by the reactive ionized cluster beam technique

Carbon nitride thin films were deposited by the reactive ionized cluster beam (RICB) technique. Fourier transform infrared (FTIR) transmission analysis shows that no marked IR peak exists for the film deposited without nitrogen, whereas a broad peak in the range 1000- and a peak due to the C3pt- 1pt- -1pt-N triple bonds are present for the films deposited with nitrogen. Both FTIR and Raman measurements obviously suggest that C1pt-N single bonds exist when nitrogen is introduced. The intensity of this band rises with increasing nitrogen pressure. The above results are also supported by x-ray photoelectron spectroscopy (XPS) analysis.