Pit Ho Patrio Chiu

A study of the size effect on the temperature-dependent resistivity of bismuth nanowires with rectangular cross-sections

Rectangular cross-section bismuth nanowires with dimensions of 50 nm by 70–200 nm (thickness by width) were fabricated using an electron beam writing technique. Individual nanowire measurement is possible using this method. The resistivities of the 50 nm thick nanowires were dependent on line width. The measured resistivity of 70, 120 and 200 nm wide nanowires was 4.05 × 10−3, 2.87 × 10−3 and 2.30 × 10−3 Ω cm at 300 K respectively. Temperature-dependent resistance measurements indicated that the electrical conductivity of the Bi nanowires was carrier dependent, and the carrier density decreased at low temperature, showing that the all the Bi nanowires exhibited semiconductor behaviour. The size-dependent resistivity of the Bi nanowires was an indication of the ordinary size effect in the one-dimensional nanowire, where the carrier mobility was grain boundary scattering dominated.

Nonlinear current-voltage characteristics of bismuth nanodot structures

Bismuth (Bi) nanodot structures have been fabricated using the proximity effects of electron-beam writing technique. Bi nanodots, each 100nm in diameter, were fabricated on an oxidized silicon substrate with a 200nm thick silicon oxide layer. Current-voltage (I-V) measurements were performed under low vacuum condition at temperatures from 77 to 300K. The measurement results showed significant nonlinearities with symmetric resistance peaks, indicating the existence of energy level spacing within the nanodot structures. The successful observation of energy level spacing in such a large nanodot is due to the small effective mass of Bi material, which leads to measurable energy level spacing.

Electric field distribution in InGaAs/InP PIN photodetector

In the present work, electric field distribution of an InGaAs/InP PIN mesa type photodetector is studied by employing electron beam induced current (EBIC) technique using a scanning electron microscope (SEM) with consideration of electron-hole pair generation volume. Depletion width and p+/n- metallurgical junction location are determined in the experiment.

Effects of active learning classrooms on student learning: a two-year empirical investigation on student perceptions and academic performance

ABSTRACT Recent studies on active learning classrooms (ACLs) have demonstrated their positive influence on student learning. However, most of the research evidence is derived from a few subject-specific courses or limited student enrolment. Empirical studies on this topic involving large student populations are rare. The present work involved a large-scale two-year study that examined the effects of ACL on student perceptions of their learning experience and the relationship with academic performance in a General Education programme. An institutional survey was used to gather more than 35,000 units of student perception data from all 306 courses in the programme. Our empirical findings show that students thought courses that adopted an ACL as the key learning environment were significantly better designed and more encouraging of student creativity and innovation than courses which used regular classrooms; thus, student perceptions were improved. We are also the first to report that this positive effect on creativity and innovation is statistically unaffected by academic performance, with high, middle and low achievers all benefiting from the use of the facility. The results suggest that ACLs are better environments for nurturing innovation for all students, regardless of their academic ability.

A project-problem based learning approach for appreciating ancient cultural heritage through technologies: Realizing mystical buildings in Dunhuang Mural

This paper reports a project-problem based learning approach for motivating technically skilled students to learn and appreciate cultural heritage, a discipline which is unrelated to their own majors. A group of undergraduate students participated in this pilot project. They were placed in an interdisciplinary environment, instructed to apply 3D design and 3D printing technologies to realize ancient drawings of buildings found in the Dunhuang Mural from the Tang Dynasty, China (618–907 AD). Self-learning and peer-learning pedagogies were adopted in the project, they guided students to overcome the challenges and attain the project outcomes. All participants had successfully completed the assigned tasks and their achievements were recognized in a public exhibition. From the qualitative and quantitative feedbacks, participants reported statistically significant improvement in their perceptions of learning and appreciating cultural heritage through the project. It also revealed that peer-learning was essential for them to complete the 3D designs, while self-learning was adopted in learning cultural heritage knowledge.