Advances in Science and Technology Vol. 51

Abstract: New materials such as langasite and langanate crystals present some interesting perspectives for acoustic wave devices due to strong piezoelectric coefficients and due to the opportunity to work through a wide range of temperature. Theoretical formulations for temperature coefficients and electromechanical coupling coefficients of resonators are given in the case of thickness modes of vibration. Results are computed using two data sets of elastic, piezoelectric and dielectric constants. Orientations of BAW microresonators which give zero frequency shift versus temperature at 600°C are determined to serve as high temperature nanobalances.

Abstract: Constraction and characteristics of sorption polymeric relative humidity sensors, sorption SiOx microhumidity sensors, and condensation type (dew point) sensors are compared. The characteristics of the sensors are examined in dew point range from -80 to +20oC. An integrated multifunctional humidity sensor, for measurements in wide humidity range at different conditions is developed. The sensors are intended for use in various branches of industry, and in scientific researches.

Abstract: Nanotechnology is occurring simultaneously in almost every field with strong interdisciplinary applications which have unique and important characteristics for potential novel and high performance devices. Quantum dots grown by epitaxial self-assembly via Stranski- Krastanov growth mode have many favorable properties for infrared sensing. Because of their very small size and three-dimensional confinement, the electronic energy levels are quantized and discrete. These quantum effects lead to a unique property, “phonon bottleneck”, which might enable the high operating temperature of infrared sensing which usually requires cryogenic cooling. Here we report a focal plane array (FPA) based on an epitaxial self-assembled quantum dot infrared detector (QDIP). The device structure containing self-assembled In0.68Ga0.32As quantum dots with a density around 3×1010 cm-2 was grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). Using different structures, we successfully developed QDIPs with a peak photoresponse around 5 μm and 9 μm. High peak detectivities were achieved at 77 K from both QDIPs. By stacking both device structures, we demonstrated a two-color QDIP whose peak detection wavelength could be tuned from 5 μm to 9 μm by changing the bias. 256×256 detector arrays based on 5 μm and 9 μm-QDIPs were fabricated with standard photolithography, dry etching and hybridization to a read-out integrated circuit (ROIC). We demonstrated thermal imaging from our FPAs based on QDIPs.