Papers by N. Ghalichechian
12th European Conference on Antennas and Propagation (EuCAP 2018), 2018
We report a distributed loaded line phase shifter based on a new class of electro-thermally actua... more We report a distributed loaded line phase shifter based on a new class of electro-thermally actuated RF MEMS devices using paraffin phase-change material (PCM). Paraffin is a low loss (tan δ = 6.6×10 −4) mechanical phase-change material that exhibits a 15% volumetric change through its solid-liquid transition. Due to its unique electrical and mechanical properties, paraffin PCM variable capacitors exhibit a very low loss which is critical in designing reconfigurable structures. Here, a low-loss paraffin PCM based true-time delay, continuously-tunable phase shifter is designed and optimized. A figure-of merit of 71.8 • /dB is achieved while maintaining a return loss more than 12 dB. Designed phase shifter has a maximum insertion loss of 5 dB for a 360 • phase shift. Electro-thermo-mechanical performance of the paraffin PCM device is studied by carrying out a fully coupled multiphysics simulation. Maximum displacement of 0.8 µm is achieved with a 2.6 µm-thick paraffin film. A new fabrication method for the deposition of the thin paraffin film is developed and a fabrication process for the device is presented.
IEEE Transactions on Device and Materials Reliability, 2004
An approach using interdigitated capacitors for electrical characterization of CYCLOTENE, a spin-... more An approach using interdigitated capacitors for electrical characterization of CYCLOTENE, a spin-on low-k benzocyclobutene (BCB)-based polymer is introduced and the effect of moisture uptake is investigated. The dielectric constant of CYCLOTENE is extracted from capacitance measurements with a systematic error less than 0.1%, giving an average value of 2.49 with a standard deviation of 1.5%. The dielectric constant increases by 1.2% after a humidity stress of 85% RH at 85 C. The-characteristics of CYCLOTENE show a dependency of breakdown strength and leakage current on the geometrical dimensions of the device under test. A breakdown strength of 225 V/ m and 320 V/ m for 2-m and 3-m finger spacing, respectively, and a leakage current of a few to tens of pA are measured. The-characteristics degrade drastically after the humidity stress, showing a breakdown strength of 100 V/ m and 180 V/ m for 2-m and 3-m finger spacing, respectively, and a maximum increase in the leakage current as large as one order of magnitude. The maximum performance and long-term reliability of an electric micromachine are adversely affected by the degradation of the breakdown voltage and the leakage current after moisture absorption. It is expected, however, that the electrical efficiency is improved using BCB-based polymers with negligible dependency on moisture absorption.
This study aimed to identify the practice extent of mathematics and science teachers of professio... more This study aimed to identify the practice extent of mathematics and science teachers of professional development activities, its sources and obstacles at elementary schools in Najran, and its relationship with specialty, gender, number of training courses. To achieve the study aims, the research questionnaire was prepared and consisted of (70) items distributed to three fields related to the activities, sources, and obstacles of the professional development in curriculum developed of the American McGraw Hill Education. Validity of the questionnaire was asserted by submitting it to a number of specialist arbitrators. Reliability was also verified and Cronbach Alpha correlation coefficient was (0.97). The study sample consisted of (201) teachers among which (103) mathematics teachers and (98) science teachers who were all teaching the developed mathematics and science curricula at the elementary schools in Najran during the academic year 2014/2015. Findings showed that the practice level of teachers' practice degree of professional development activities was moderate. The sources of which they receive professional development programs and obstacles they face were moderate, too. Results indicated that there were no statistically significant differences due to specialization and training courses, while there were significant differences (α=0.01) among teachers with regard to the practice degree of professional development activities and the number of training courses due to gender in favor of females. The study recommended paying attention to the programs of teachers' professional development and their participation to meet their needs and requirements to attend conferences, seminars, workshops at the universities.
Integration of low dielectric constant Benzocyclobutene (BCB) film with deep etched structures in... more Integration of low dielectric constant Benzocyclobutene (BCB) film with deep etched structures in silicon allows the fabrication of MEMS devices with low parasitic loss. A fabrication process is developed for integration of thin BCB film and deep anisotropically-etched grooves in silicon using potassium hydroxide (KOH).
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Papers by N. Ghalichechian