An atomic force microscope (AFM) is used to measure the magnitude of the effective longitudinal piezoelectric constant (d33) of thin films. Measurements are performed with a conducting diamond AFM tip in contact with a top electrode. The interaction between the tip and electric field present is a potentially large source of error that is eliminated through the use of this configuration and the conducting diamond tips. Measurements yielded reasonable piezoelectric constants of X-cut single-crystal quartz, thin film ZnO, and nonpiezoelectric SiO2 thin films.

This article presents a study of the quasi-longitudinal optical and quasi-transverse optical modes in wurtzite AlN which originate from the interaction of phonons belonging to the A1 and E1 symmetry groups. In order to analyze the allowed quasi as well as pure Raman modes, the modes were observed in a rotating crystallographic coordinate system, and the Raman tensors of the wurtzite crystal structure were calculated as a function of the crystallographic rotation. The frequencies of the quasimodes of wurtzite AlN were also analyzed in terms of the interaction of the polar phonons with the long range electrostatic field model. The experimental values of the Raman frequencies of the quasiphonons concur with these expected from the model, implying that the long range electrostatic field dominates the short range forces for polar phonons in AlN.

An atomic force microscope (AFM) is used to measure the magnitude of the effective longitudinal piezoelectric constant (d33) of thin films. Measurements are performed with a conducting diamond AFM tip in contact with a top electrode which is driven by an externally applied voltage. The interaction between the tip and electric field present is a potentially large source of error that is eliminated through the use of this configuration and the conducting diamond tips. Measurements yielded reasonable piezoelectric constants of X-cut single crystal quartz, thin film ZnO, Pb(Zr,Ti)O3 (Zr/Ti = 30/70), and nonpiezoelectric amorphous SiO2 thin films. The system was also used to measure d33 hysteresis loops for Pb(Zrx,Ti1−x)O3 thin films.

Imaging of the phase and magnitude of the piezoelectric strain in Pb͑Zr 0.3 , Ti 0.7 ͒O 3 ͑PZT͒ capacitors is performed with an atomic force microscope. The imaging reveals a significant spatial dependence of the ferroelectric properties of both fatigued and unfatigued PZT films. We propose that the variation is related to the domain structure of the PZT. Through the measurement of local piezoelectric hysteresis loops and imaging of the piezoelectric strain, areas are observed in fatigued PZT that exhibit hysteresis loops shifted along the polarization axis. In some regions of fatigued samples, the hysteresis loops are shifted such that both remanent points of the hysteresis curve have the same polarization direction. These results have important implications for the scalability of nonvolatile ferroelectric random access memory to higher device densities.

Articles you may be interested inComposite-layered solid-state field controlled emitter for a better control of the cathode surface barrier J. Vac. Sci. Technol. B 23, 824 (2005); 10.1116/1.1864065Field emission characteristics of boron nitride films deposited on Si substrates with cubic boron nitride crystal grains J.Cold cathode structures have been fabricated using AlN and graded AlGaN structures ͑deposited on n-type 6H-SiC͒ as the thin film emitting layer. The cathodes consist of an aluminum grid layer separated from the nitride layer by a SiO 2 layer and etched to form arrays of either 1, 3, or 5 m holes through which the emitting nitride surface is exposed. After fabrication, a hydrogen plasma exposure was employed to activate the cathodes. Cathode devices with 5 m holes displayed emission for up to 30 min before failing. Maximum emission currents ranged from 10-100 nA and required grid voltages ranging from 20-110 V. The grid currents were typically 1 to 10 4 times the collector currents.