An Extended UTAUT Model for the Study of Negative User Adoption Behaviours of Mobile Commerce

An extended Unified Theory of Acceptance and Use of Technology (UTAUT) for mobile commerce (m-commerce) was empirically tested using data collected from a web survey distributed to and through the Hong Kong undergraduates and postgraduates. The partial least squares (PLS) technique of the structural equation modeling (SEM) was used to evaluate the causal model and the confirmatory factor analysis (CFA) was performed to examine the reliability and validity of the measurement model. Findings indicated that the new construct of Disturbance Concerns (DC) is a significant factor affecting users’ behavioural intention. This study aims to understand both the positive and negative factors that can significantly explain user acceptance intention and use behaviour so that service providers can adjust their strategies for providing successful m-commerce services. It also provides a base for further research on the user acceptance models of new information systems

User Adoption Behaviors of Mobile Commerce: China VS Taiwan

This study aims to further test the technology acceptance model for mobile commerce (m-commerce) in China and Taiwan. Data was collected from 156 college students in Macau (China) and 173 college students in Kaohsiung (Taiwan). Exploration factor analysis is performed to examine the reliability and validity of the model; regression analysis is performed to access the relationship between behavior intention and each factor in these two markets; and t-tests are performed to compare the difference in the means from Chinese and Taiwan college students. This study finds out that even there is not significant culture difference between China and Taiwan, there is a significant difference in the means of social influence between these two markets

Low temperature silicon-based epitaxy for solar cells applications

Epitaxial silicon (Si)-based solar cell technology is an attractive alternative for large-scale and high-throughput manufacturing of cost-effective solar cells through reduced Si consumption. However, due to the optical losses related to reduced Si thickness, it is critical to improve the short-circuit current density (Jsc) of the solar cell. Thus, it becomes imperative to explore a robust scheme to achieve high Jsc for the epitaxial Si solar cells to realize its full potential. The aim of this work is to design, fabricate and characterize epitaxial emitter (epi-emitter) Si solar cells that yield higher Jsc. Three schemes are investigated and compared to determine the most effective scheme to improve the Jsc of the solar cells. Firstly, low temperature Si epitaxy technique is employed to form epi-emitter Si solar cells using bulk crystalline Si substrates, with POCl3 diffused solar cells as the control cell. Next, to lower the contact resistance, the effects of back germanium (Ge) epilayer on an active epitaxial cell performance have been studied; using both highly doped and optimally doped Si substrates. Finally, the effects of architectural and peripheral modifications on the performance of epi-emitter Si solar cells are evaluated. An alternative approach has been demonstrated to grow phosphorus-doped epitaxial Si emitter by ASM 2000 at low temperature (T <700°C). A PCEpseudo of (10.2 ± 0.2)% and Jsc of 28.8 mA/cm2 has been achieved for the solar cell with epi- emitter grown at 700°C, in the absence of surface texturization, antireflective coating, and back surface field enhancement, without considering front contact shading. Secondary ion mass spectroscopy revealed that lower temperature Si epitaxy yields a more abrupt p-n junction; suggesting potential applications for radial p-n junction wire array solar cells. Mechanical twinning observed in the epi- emitter improves the optical absorbance of the cells. Based on the results, a higher PCE can be achieved by increasing the Jsc through optimization of the contact. In order to lower the contact resistance with back aluminum (Al) contact, the epi- emitter Si solar cells have been fabricated using a back Ge epilayer on highly boron (B)-doped Si substrates. The fabrication of these cells involved a two-step epitaxy process to grow the back Ge epilayer, followed by the front side epi- emitter. Control samples are fabricated under identical conditions for comparison. It is found that Jsc of the epi-emitter cell with back Ge epilayer and back B-doped Ge epilayer is ~12.4% and ~16.6% higher than that of the control cell, respectively. The performance of epi-emitter Si solar cells with back Ge epilayer grown on optimally doped Si substrates is compared to the cells with conventional BSF scheme. A maximum PCE of 10.2% and Jsc of 27.2 mA/cm2 have been achieved for the epi-emitter cell with back Ge epilayer. When compared to the control cell, a remarkable relative Jsc improvement of ~24.3% is seen. Moreover, the cells with back Ge epilayer exhibit a significant improvement in EQE response around the infrared region due to enhanced charge separation by the Si/Ge heterojunction, when compared to the cells with BSF epilayer. It is also found that the cell with back Ge epilayer and the cell with BSF epilayer have comparable PCEs. The effect of architectural and peripheral modifications of epi-emitter Si solar cells has been studied. Firstly, the synergistic approach of direct FIB etching and FGA step on the defective epi-emitter layer forms Si nanocone array with Si nanocrystals. An absolute Jsc improvement of 0.3 mA/cm2 is observed with a very small textured surface of ~0.1% and the presence of Si nanocrystals. This suggests the potential of using FIB etch and FGA step to improve the light trapping capability for epitaxial Si solar cells. In addition, such direct patterning technique is ideal for very thin cells that are incompatible with lithography. Secondly, we have demonstrated that the reduced broadband reflectance and the PL property of embedded Si nanocrystals in the Si3N4 layer of the bilayer ARC can improve the PCE of epi-emitter Si solar cells. It is found that the Si nanocrystals could downshift high-energy ultraviolet photons to lower-energy photons to enhance the overall PCE. A relative Jsc enhancement of 12.5% is observed for the epi-emitter cell with bilayer ARC and back Ge epilayer as compared to the control cell with back Ge epilayer. However, front surface recombination, due to poor passivation between the interface of epi-emitter and the Si nanocrystals, may have caused the PCE degradation for the cell with bilayer ARC and back Ge epilayer. To minimize losses due to front surface recombination and enhance the PCE of epi-emitter Si solar cells in future studies related to architectural and peripheral modifications, we recommend using remote hydrogen plasma passivation to passivate the surface of the Si nanocrystals.DOCTOR OF PHILOSOPHY (EEE

Metal gate for advanced CMOS applications

A potential metal gate candidate must possess good thermal stability to withstand high anneal temperature and it must also have an effective workfunction (EWF) that is near to the silicon band edges. DC sputtered tungsten nitride (W2N) metal gate on high- K dielectrics is investigated for this application. Rutherford backscattering (RBS) data reveals that oxygen incorporation into tungsten nitride films occurred after the rapid thermal anneal (RTA) treatment and yet the resulting tungsten oxynitride (W0.377O0.322N0.301) maintained its conductivity. Nonetheless, the effective gate oxide thickness increases with the presence of the oxynitride (SiON). To rectify this issue and reduce the leakage current density, a ruthenium (Ru) capping layer was introduced.Master of Engineering (MSE

A model for the study of user adoption behaviours of mobile commerce

With strong computing power and efficient data networks, new mobile phones are sophisticated enough for smoothly surfing the internet and conducting electronic commerce as on the desktop computers, there should have significant opportunities and growth of mobile commerce. However, the user acceptance of m-commerce is below expectation (Harris et al., 2005). Researches of the user acceptance of m-commerce have proven the positive user adoption determinants based on the user acceptance models of information systems (IS), but only few explore the negative adoption factors. This paper extends the unified theory of acceptance and use of technology (UTAUT) model for the study of the negative emotion and behaviour that affects the user acceptance of m-commerce. The extended UTAUT model aims to help m-commerce service providers to understand both the positive and negative factors that can significantly explain user adoption intention and use behaviour so that they can adjust their strategies for providing successful m-commerce services. It also provides an extended base for further research on the user acceptance models of new IS.

A Model for the study of user adoption behaviours of mobile commerce

With strong computing power and efficient data networks, new mobile phones are sophisticated enough for smoothly surfing the internet and conducting electronic commerce as on the desktop computers, there should have significant opportunities and growth of mobile commerce. However, the user acceptance of m-commerce is below expectation (Harris et al., 2005). Researches of the user acceptance of m-commerce have proven the positive user adoption determinants based on the user acceptance models of information systems (IS), but only few explore the negative adoption factors. This paper extends the unified theory of acceptance and use of technology (UTAUT) model for the study of the negative emotion and behaviour that affects the user acceptance of m-commerce. The extended UTAUT model aims to help m-commerce service providers to understand both the positive and negative factors that can significantly explain user adoption intention and use behaviour so that they can adjust their strategies for providing successful m-commerce services. It also provides an extended base for further research on the user acceptance models of new IS.10 page(s

Enhanced conversion efficiency for Si nanowire–organic hybrid solar cells through the incorporation of organic small molecule

We demonstrate high-efficiency hybrid solar cells based on heterojunctions formed between n-type silicon nanowires (SiNWs) and p-type organic semiconductors fabricated using a simple solution-based approach. Two types of devices have been fabricated with different organic materials used, namely poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and a small molecule, 2,2',7,7'-tetrakis(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD). The cells are characterized and compared in terms of their physical characteristics and photovoltaic performance. Using SiNWs of the same length of 0.35 µm, it is found that the SiNWs/Spiro cells exhibit a power conversion efficiency of 10.3%, which is higher than the 7.7% of SiNWs/PEDOT cells. The results are interpreted in terms of the ability of the two organic semiconductors to fill the gaps between the SiNWs and the optical reflectance of the samples. The degradation of the SiNWs/Spiro cells is also studied and presented

High efficiency planar Si/organic heterojunction hybrid solar cells

We present an efficient hybrid solar cell based on poly (3,4-ethylene-dioxythiophene):polystyrenesulfonate and planar Si with (100) and (111) orientations. The effect of Si surface native oxide on cell performance is studied. Compared to cell with hydrogen-terminated Si surface, the cell with oxygen-terminated Si surface reveals a 530-fold increase in power conversion efficiency (PCE) from 0.02% to 10.6%. The formation of SiOx-Si bonds poses a net positive surface dipole which leads to a favorable band alignment for charge separation. However, thicker oxide degrades cell performance due to higher series resistance. This study demonstrates the highest PCE reported to-date in this field.Published versio

Si nanowires organic semiconductor hybrid heterojunction solar cells toward 10% efficiency

High-efficiency hybrid solar cells are fabricated using a simple approach of spin coating a transparent hole transporting organic small molecule, 2,2′,7,7′-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (Spiro-OMeTAD) on silicon nanowires (SiNWs) arrays prepared by electroless chemical etching. The characteristics of the hybrid cells are investigated as a function of SiNWs length from 0.15 to 5 μm. A maximum average power conversion efficiency of 9.92% has been achieved from 0.35 μm length SiNWs cells, despite a 12% shadowing loss and the absence of antireflective coating and back surface field enhancement. It is found that enhanced aggregations in longer SiNWs limit the cell performance due to increased series resistance and higher carrier recombination in the shorter wavelength region. The effects of the Si substrate doping concentrations on the performance of the cells are also investigated. Cells with higher substrate doping concentration exhibit a significant drop in the incident photons-to-current conversion efficiency (IPCE) in the near infrared region. Nevertheless, a promising short circuit current density of 19 mA/cm2 and IPCE peak of 57% have been achieved for a 0.9 μm length SiNWs cell fabricated on a highly doped substrate with a minority-carrier diffusion length of only 15 μm. The results suggest that such hybrid cells can potentially be realized using Si thin films instead of bulk substrates. This is promising towards realizing low-cost and high-efficiency SiNWs/organic hybrid solar cells