Pulsed Thermal Processing Research Articles

Direct processing of PbZr0.53Ti0.47O3 films on glass and polymeric substrates

This work reports on direct crystallization of PbZr0.53Ti0.47O3 (PZT) thin films on glass and polymeric substrates, using pulsed thermal processing (PTP). Specifically, xenon flash lamps deliver pulses of high intensity, short duration, broadband light to the surface of a chemical solution deposited thin film, resulting in the crystallization of the film. Structural analysis by X-ray diffraction (XRD) and transmission electron microscopy show the existence of perovskite structure in nano-sized grains (≤5 nm). Local functional analysis by band excitation piezoelectric spectroscopy and electrostatic force microscopy confirm the presence of a ferroelectric phase and retention of voltage-written polarization for multiple days. Based on structural and functional analyses, strategies are discussed for optimization of pulse voltage and duration for the realization of crystalline ferroelectric thin films. For ∼200 nm-thick PZT films on glass substrates, 500 μs-long pulses were required for crystallization, starting with 100 pulses at 350 V, 10 or 25 pulses at 400 V and in general lower number of pulses at higher voltages (resulting in higher radiant energy). Overall power densities of >6.4 kW/cm2 were needed for appearance of peaks corresponding to the perovskite phase in the XRD. Films on glass processed at 350–400 V had a higher degree of 111-oriented perovskite grains. Higher applied radiant energy (through increased pulse voltage or count) resulted in more random and/or partially 001-oriented films. For ∼1 μm-thick PZT films on polymeric substrates, 10 to 25 250 μs-long pulses at voltages ranging between 200 to 250 V, corresponding to power densities of ∼2.8 kW/cm2, were optimal for maximized perovskite phase crystallization, while avoiding substrate damage.

Pulsed-thermal processing of chemically synthesized FePt nanoparticles

The disordered face-centered-cubic A1 to the chemical ordered face-centered-tetragonal L10 phase transformation of chemically synthesized magnetic FePt nanoparticles has been studied in the millisecond regime using a pulsed high-density plasma arc light source. Under select annealing conditions, relatively high magnetic coercivities (Hc) and anisotropies (Hk) of FePt nanoparticles were obtained with the millisecond pulse processing without significant sintering of the nanoparticles.

Ferroelectric lead niobate films by pulsed thermal processing

Ferroelectric lead niobate (PbNb2O6) exists in an orthorhombic phase at room temperature. The fabrication of lead niobate in this ferroelectric form has often been reported to be difficult due to the stabilization of nonferroelectric phases during processing. In this letter, the stabilization of the orthorhombic phase in magnetron sputtered lead niobate films using ‘‘pulsed thermal processing’’ is reported, and various processing factors which influence the destabilization of this phase are discussed. The room-temperature dielectric constant and loss tangent of the resulting films at 1 kHz were 320 and 0.4, respectively. Polarization versus electric-field hysteresis loops showed no saturation, with a remanent polarization of 15 μC/cm2 and a coercive field of 500 kV/cm. The films were highly resistive with a dc conductivity of 1−10 Ω−1 cm−1 at 300 K.