Issue No. 1, June

Abstract

Screen-printing technology provides a convenient method in fabricating thick-film conductive circuits and devices in the past few decades. Conventionally, piezoelectric thick-film is printed on alumina substrate with high mechanical Q-factor and resonates at higher frequency outside the range of ambient vibration. As the piezoelectric charge generation is proportional to the mechanical stress on the material, therefore the substrate can be removed in order to lower the natural frequency of the structure. In this paper, a series of piezoelectric ceramic cantilevers were fabricated in the form of free-standing cantilever. An additional layer of ceramic was also introduced to the upper and lower electrode to prevent delamination. The issue of zero resultant stress for the sandwiched piezoelectric cantilever was solved by repeating the electrode-PZTelectrode layer to form a multilayer structure. It was found from the experiment that an electrical output power of 32 μW was generated when it operates at its resonant frequency at 403 Hz.

Abstract

In contrast to the Moore’s Law exponential growth in CMOS transistor areal density, computer clock speeds have been frozen since 2003 due to excessive power dissipation. We present the development of a new digital switch, the PiezoElectronic Transistor (PET), designed to circumvent the speed and power limitations of the CMOS transistor. The PET operates on a novel principle: an electrical input is transduced into an acoustic pulse by a piezoelectric (PE) actuator, which, in turn, drives a continuous insulator-to-metal transition in a piezoresistive (PR) channel, thus switching on the device. Predictions of theory and simulation, assuming bulk materials properties can be approximately retained at scale, are that PETs can operate at one-tenth the present voltage of CMOS technology and 100 times less power, while running at multi-GHz clock speeds. CMOS-like computer architectures, such as a simulated adder, can be fully implemented. Materials development for PE and PR thin films approaching the properties of bulk single crystals, and a successful fabrication scheme, are the key to realizing this agenda. We describe progress in developing PE films (where d33 is critical) and PR films (characterized by conductance and ON/OFF ratio) of demonstration quality. A macroscopic-scale PET has been built to demonstrate PET viability over large numbers of switching cycles. The perspective for the development of pressure-driven electronics will be outlined.

Abstract

The charge density wave order in titanium diselenide is unusual in that it is characterized by a breakdown of inversion symmetry as well as translational symmetry, leading to the emergence of a chiral crystal structure. This novel state of matter was recently described theoretically in terms of the simultaneous and cooperative onset of both charge and orbital order. Here, we discuss the analysis of recent X-ray diffraction and related measurements on 1T-TiSe₂ in terms of the predictions of that theoretical model. It is show that the experimental observations agree with the expectations from an emerging combined charge and orbital ordered phase.