Dezhang Zhu

Cathodoluminescence and ion beam analysis of ion-implanted combinatorial materials libraries on thermally grown SiO2

A method combining ion implantation and physical masking technique has been used to generate material libraries of various ion-implanted samples. Ion species of C, Ga, N, Pb, Sn, Y have been sequentially implanted to an SiO2 film grown on a silicon wafer through combinatorial masks and consequently a library of 64 (2(6)) samples is generated by 6 masking combinations. This approach offers rapid synthesis of samples with potential new compounds formed in the matrix, which may have specific luminescent properties. The depth-resolved cathodoluminescence (CL) measurements revealed some specific optical property in the samples correlated with implanted ion distributions. A marker-based technique is developed for the convenient location of sample site in the analysis of Rutherford backscattering spectrometry (RBS) and proton elastic scattering (PES), intended to characterize rapidly the ion implanted film libraries. These measurements demonstrate the power of nondestructively and rapidly characterizing composition and the inhomogeneity of the combinatorial film libraries, which may determine their physical properties

γ-ray irradiation effects of Au/PbTiO3/YBa2Cu3O7-δ capacitors under different bias voltage

Abstract Total dose radiation effects on Au/PbTiO 3 /YBa 2 Cu 3 O 7− δ (YBCO) capacitors fabricated by pulsed excimer laser deposition (PLD) on SrTiO 3 substrates have been investigated. Capacitance–voltage characteristics and the retained polarization property of the capacitors have been measured before and after γ-ray irradiation. The +4 and 0 V bias was applied across the capacitors during the irradiation. The results showed that with the increment of the total dose, the retained polarization, dielectric constant and the coercive field decreased. The results have been interpreted by radiation-induced positive charges and a defect trap model.

Characteristics of Au/PbZr0.52Ti0.48O3/YBa2Cu3O7−δ capacitors fabricated on LaAlO3 and Y2O3-stabilized ZrO2 substrates during irradiation

PbZT(0.52)Ti(0.48)O(3) (PZT)/YBa2Cu3O7-delta (YBCO) structures were fabricated on LaAlO3 and Y2O3-stabilized ZrO2 (YSZ) substrates by a pulsed-excimer-laser deposition method. The total dose effects on the Au/PZT/YBCO ferroelectric capacitors were considered by measuring the capacitance-voltage (C-V) characteristics and the retained polarization properties of the capacitor before and after gamma-ray irradiation. The results show that, with an increase of irradiation dose, for a ferroelectric capacitor which was fabricated on a LaAlO3 substrate, the retained polarization Delta P and the dielectric constant epsilon decreased, but the absolute value of the negative and positive coercive fields increased. For a ferroelectric capacitor which was fabricated on a YSZ substrate, Delta P and epsilon also decreased while the coercive fields drifted towards the positive voltage direction. All these facts are due to the effect of charges trapped by defects in the PZT layer and the interface of the capacitor during irradiation.

Combinatorial ion synthesis and ion beam analyses of materials libraries on thermally grown SiO2

Abstract We first report a method combining ion implantation and physical masking to generate material libraries of various ion-implanted samples. This approach offers rapid synthesis of samples with potential new compounds formed in the matrix, which may have specific luminescent properties. The depth-resolved cathodoluminescence (CL) measurements, accompanied with Rutherford backscattering spectrometry (RBS) and proton elastic scattering (PES) revealed some specific optical properties in the samples correlated with implanted ion distributions. These measurements are capable of nondestructively and rapidly characterizing the composition and the inhomogeneity of the combinatorial film libraries, which may determine their physical properties.

Total dose radiation effects of Pt/PZT/Pt ferroelectric capacitors fabricated by PLD method

In order to study total dose radiation effects of PbZrxTi1-xO3 (PZT) film made with the pulsed excimer laser deposition (PLD) technique, hysteresis loops and capacitance-voltage (C-V) curves of PZT film capacitors have been measured before and after gamma-ray irradiation. The results show that, in a range of 0-2 x 10(5) Gy (Si), with increasing total dose, the remanent polarization 2P(r) increased while dielectric constant epsilon decreased. This can be explained by charges trapped by some defects during irradiation.

Monte Carlo simulation of concentration distribution at Ni3Al-5 at.% Mg grain boundary

This work has applied the embedded atom method (EAM) to calculate concentration distribution of Mg. Ni and Al at a Ni3Al-5 at.% Mg grain boundary. and the Mg-induced distortion energies at the grain boundary, the bulk and the free surface. The calculated concentration distributions show that Mg segregation is present with Al-depletion and Ni-enrichment at the grain boundary. The cause might be not only that at the same zone, the Mg-induced distortion energy in the site of Al is always negative and lower than that of Ni. but also that the Mg-induced distortion energy in the Al site at the grain boundary is the lowest among those at all zones

Retardation of strain relaxation in Si/SiGe/Si heterostructures during high temperature oxidation

Abstract The variations of strain stored in Si/Si1−xGex/Si heteroepitaxial system with SiGe thickness below its critical thickness during high temperature oxidation (in O2–C2H2Cl2 ambient) or annealing (in Ar ambient) processing were investigated by ion channeling angular scan and high resolution X-ray diffraction. The retardation of strain relaxation in an oxidized sample compared with that in an Ar-annealed sample was observed. The depth profiles of Ge determined by SIMS indicated that Ge diffusion in the annealed sample is larger than that in the oxidized sample. The reduced diffusion of Ge in the oxidized sample compared to the Ar-annealed sample is responsible for retardation of strain relaxation.

Different strain relaxation mechanisms in strained Si/Si1-xGex/Si heterostructures by high dose B+ and BF2+ doping

Strained Si/Si0.8Ge0.2/Si heterostructures are implanted at room temperature with 7.5 keV B+ and 33 keV BF2+ ions to a high dose of 2×1015 ions/cm2, respectively. The samples are subsequently subjected to three-step anneals (spacer anneal, oxidation anneal and rapid thermal anneal), which are used to simulate a real fabrication process of SiGe-based MOSFET devices. The damage induced by implantation and its recovery are characterized by 2 MeV 4He+ RBS/channeling spectrometry. A damage layer on the surface is induced by B+ implantation, but BF+2 ion implantation amorphizes the surface of Si/Si0.8Ge0.2/Si heterostructure. Channeling angular scans along the 〈110〉 axial direction demonstrate that the strain stored in the SiGe layer could be nearly completely retained for the B+ implantated and subsequently annealed sample. However, the strain in the BF2+ implanted/annealed SiGe layer has decreased drastically.