Effect of AlN Seed Layer on Crystallographic Characterization of Piezoelectric AlN

Ultrathin aluminum nitride (AlN) films are of great interest for integration into nanoelectromechanical systems for actuation and sensing. Given the direct relationship between crystallographic texture and piezoelectric response, x-ray diffraction has become an important metrology step. However, signals from layers deposited below the piezoelectric (PZE) AlN thin film may skew the crystallographic analysis and give misleading results. In this work, we compare the use of a Ti or AlN seed layer on the crystallographic quality of PZE AlN. We also analyze the influence of several AlN seed layer thicknesses on the rocking curve FWHM of PZE AlN and demonstrate an larger effect of the AlN seed layer on the {\theta}-2{\theta} AlN crystallographic peak for increasing AlN seed layer thickness.Comment: 16 pages, 4 figures, 1 tabl

The Old Bailey proceedings and the representation of crime and criminal justice in eighteenth-century London

The Proceedings of the Old Bailey, published accounts of felony trials held at London’s central criminal court, were a remarkable publishing phenomenon. First published in 1674, they quickly became a regular periodical, with editions published eight times a year following each session of the court. Despite the huge number of trial reports (some 50,000 in the eighteenth century), the Proceedings, also known as the “Sessions Papers”, have formed the basis of several important studies in social history, dating back to Dorothy George’s seminal London Life in the Eighteenth Century (1925). Their recent publication online, however, has not only made them more widely available, but also changed the way historians consult them, leading to greater use of both quantitative analysis, using the statistics function, and qualitative examination of their language, through keyword searching. In the context of recent renewed interest in the history of crime and criminal justice, for which this is the most important source available in this period, the growing use of the Proceedings raises questions about their reliability, and, by extension, the motivations for their original publication. Historians generally consider the Proceedings to present accurate, if often incomplete, accounts of courtroom proceedings. From this source, along with manuscript judicial records, criminal biographies (including the Ordinary’s Accounts), polemical pamphlets such as Henry Fielding’s Enquiry into the Causes of the Late Increase of Robbers (1751), and of course the satirical prints of William Hogarth, they have constructed a picture of eighteenth-century London as a city overwhelmed by periodic crime waves and of a policing and judicial system which was forced into wide-ranging reforms in order to meet this challenge

Local non-equilibrium distribution of charge carriers in a phase-coherent conductor

We use the scattering matrix approach to derive generalized Bardeen-like formulae for the conductances between the contacts of a phase-coherent multiprobe conductor and a tunneling tip which probes its surface. These conductances are proportional to local partial densities of states, called injectivities and emissivities. The current and the current fluctuations measured at the tip are related to an effective local non-equilibrium distribution function. This distribution function contains the quantum-mechanical phase-coherence of the charge carriers in the conductor and is given as products of injectivities and the Fermi distribution functions in the electron reservoirs. The results are illustrated for measurements on ballistic conductors with barriers and for diffusive conductors.Comment: 4 pages, 2 figures, submitted to "Comptes Rendus de l'Academie des Sciences

Monoclonal antibodies against human astrocytomas and their reactivity pattern

The establishment of hybridomas after fusion of X63-Ag8.653 mouse myeloma cells and splenocytes from mice hyperimmunized against human astrocytomas is presented. The animals were primed with 5 × 106 chemically modified uncultured or cultured glioma cells. Six weeks after the last immunization step an intrasplenal booster injection was administrated and 3 days later the spleen cells were prepared for fusion experiments. According to the specificity analysis of the generated antibodies 7 hybridoma products (MUC 7-22, MUC 8-22, MUC 10-22, MUC 11-22, MUC 14-22, MUC 15-22 and MUC 2-63) react with gliomas, neuroblastomas and melanomas as well as with embryonic and fetal cells but do not recognize non-neurogenic tumors. The selected monoclonal antibodies (McAbs) of IgG1 and IgG2a isotypes are not extensively characterized but these antibodies have been demonstrated to be reactive with a panel of glioma cell lines with varying patterns of antigen distribution. Using the McAbs described above and a series of cryosections of glioma biopsies and paraffin sections of the same material as well as glioma cultures established from these, variable antigenic profiles among glioma cell populations could be demonstrated. From these results it is evident that there is not only a distinct degree of antigenic heterogeneity among and within brain tumors, but also that the pattern of antigenic expression can change continuously. Some of the glioma associated antigens recognized by the selected antibodies persist after fixation with methanol/acetone and Karnovsky's fixative and probably are oncoembryonic/oncofetal antigen(s). The data suggest that the use of McAbs recognizing tumor associated oncofetal antigens in immunohistochemistry facilitates objective typing of intracranial malignancies and precise analysis of fine needle brain/tumor biopsies in a sensitive and reproducible manner

50 nm thick AlN Films for Actuation and Detection of Nanoscale Resonators

We report on the optimization of a multilayer platinum/aluminum nitride (AlN) stack with an AlN active layer thickness of 50 nm for piezoelectric actuation in nanoelectromechanical systems (NEMS). Experiments in reactive sputtering of AlN were used to find optimal parameters for good crystallinity and low residual stress of a four layer film stack, shown in Figure 1. A direct relationship was measured between the AlN seed layer thickness and the x-ray diffraction (XRD) rocking curve’s full width at half maximum (FWHM) of the AlN active layer. However, no influence of seed layer thickness was found in double beam laser interferometric measurements of the clamped longitudinal piezoelectric coefficient d33,f, relating thickness strain from an applied electric field, of the XRD measured four layer film stacks

Local densities, distribution functions, and wave function correlations for spatially resolved shot noise at nanocontacts

We consider a current-carrying, phase-coherent multi-probe conductor to which a small tunneling contact is attached. We treat the conductor and the tunneling contact as a phase-coherent entity and use a Green's function formulation of the scattering approach. We show that the average current and the current fluctuations at the tunneling contact are determined by an effective local non-equilibrium distribution function. This function characterizes the distribution of charge-carriers (or quasi-particles) inside the conductor. It is an exact quantum-mechanical expression and contains the phase-coherence of the particles via local partial densities of states, called injectivities. The distribution function is analyzed for different systems in the zero-temperature limit as well as at finite temperature. Furthermore, we investigate in detail the correlations of the currents measured at two different contacts of a four-probe sample, where two of the probes are only weakly coupled contacts. In particular, we show that the correlations of the currents are at zero-temperature given by spatially non-diagonal injectivities and emissivities. These non-diagonal densities are sensitive to correlations of wave functions and the phase of the wave functions. We consider ballistic conductors and metallic diffusive conductors. We also analyze the Aharonov-Bohm oscillations in the shot noise correlations of a conductor which in the absence of the nano-contacts exhibits no flux-sensitivity in the conductance.Comment: 17 pages, 8 figure

Active layers of high-performance lead zirconate titanate at temperatures compatible with silicon nano- and microelecronic devices

Applications of ferroelectric materials in modern microelectronics will be greatly encouraged if the thermal incompatibility between inorganic ferroelectrics and semiconductor devices is overcome. Here, solution-processable layers of the most commercial ferroelectric compound ─ morphotrophic phase boundary lead zirconate titanate, namely Pb(Zr0.52Ti0.48)O3 (PZT) ─ are grown on silicon substrates at temperatures well below the standard CMOS process of semiconductor technology. The method, potentially transferable to a broader range of Zr:Ti ratios, is based on the addition of crystalline nanoseeds to photosensitive solutions of PZT resulting in perovskite crystallization from only 350 °C after the enhanced decomposition of metal precursors in the films by UV irradiation. A remanent polarization of 10.0 μC cm−2 is obtained for these films that is in the order of the switching charge densities demanded for FeRAM devices. Also, a dielectric constant of ~90 is measured at zero voltage which exceeds that of current single-oxide candidates for capacitance applications. The multifunctionality of the films is additionally demonstrated by their pyroelectric and piezoelectric performance. The potential integration of PZT layers at such low fabrication temperatures may redefine the concept design of classical microelectronic devices, besides allowing inorganic ferroelectrics to enter the scene of the emerging large-area, flexible electronics