35 research outputs found
Optimising the Structure of Metal-Insulator-Metal Diodes for Rectenna Applications
No full textThe work in this thesis investigates the design and fabrication of metal-insulator-metal (MIM) diodes using an ultrathin organic insulator. The organic insulating layer was found to be compact, highly conformal, and uniform, effectively overcoming the main design challenge in MIM diodes. The fabricated diodes have strong nonlinear current-voltage characteristics with a zero-bias curvature coefficient and a voltage responsivity among the best values reported in the available literature. The fabrication process is simple and carried out at low temperature, which is cost effective, and can potentially be ported to large-area roll-to-roll manufacturing. An encapsulation method to prevent MIM junctions’ degradation has also been developed.
Following the successful production of these MIM devices on a rigid substrate, with the fabrication only requiring low-temperature processing, the diodes were successfully fabricated on a flexible substrate with results similar to those fabricated on a rigid substrate. The flexible substrate diodes show no significant degradation in performance when stressed in a one-off bending experiment, although extreme mechanical stress testing does produce some loss in quality.
Also, an elegant method for matching the impedance of an antenna to that of a MIM diode was successfully developed, for optimal external conversion efficiency where the diodes are used in a rectenna device. The responsivity of the impedance-matched rectenna is approaching an order of magnitude higher than that of a control device without a matching network. The fabrication, electrical characterisation and physical analysis of both the MIM diodes and rectennas are discussed in detail in this thesis
Novel low-cost ultra-high-speed diodes for electromagnetic energy harvesting
No full textThis work presents the fabrication of novel high-frequency low-cost metal-insulator-metal (MIM) diodes with the dielectric (insulating) layer formed using a chemical approach at low temperature, rather than using the more aggressive techniques typical of the semiconductor industry. This device is a useful component in a wide range of applications, including radio frequency identification (RFID), high frequency detectors and mixers, and electromagnetic energy harvesting as in (Y. Pan, C. V. Powell, A. M. Song, and C. Balocco, “Micro Rectennas: Brownian Ratchets for Thermal-Energy Harvesting”, Appl. Phys. Lett. 105, 253901, 2014)
High-performance rectifiers fabricated on a flexible substrate
No full textWe report on the fabrication and testing of metal-insulator-metal (MIM) diodes on a flexible substrate where the thin insulating layer self-assembles as a monolayer sandwiched between the two metal electrodes. The current-voltage characteristic has a strong asymmetry and non-linearity at zero-bias. The diodes have a typical zero-bias resistance of 80 kΩ, a zero-bias curvature coefficient of 5.5V-1, and a voltage responsivity of 3.1 kV/W at a frequency of 1 GHz. The fabrication yield was over 90%, and an encapsulation method to prevent MIM junction degradation has also been developed. The diodes show no significant degradation in performance when the substrate is stressed in a one-off bending experiment, although extensive testing does produce some loss in quality. The fabrication process is simple, cost effective, and carried out at low temperature, opening up the possibility of roll-to-roll volume manufacturing of fast MIM diodes
High-frequency metal-insulator-metal (MIM) diodes for thermal radiation harvesting
No full textThe fabrication of low-cost metal-insulator-metal (MIM) diodes using a self-assembled monolayer as the insulating layer is presented. DC and AC analysis show that the diodes have excellent non-linear current voltage characteristics compared to those typically reported, with a zero-bias curvature coefficient ranging from 0.5 V-1 to 5.4 V-1, voltage responsivity of 1.9 kV/W at a frequency of 1 GHz. The process developed for fabricating these diodes is simple, cost effective, and can potentially be used in the roll-to-roll manufacturing of MIM diodes. Reliability tests performed on the fabricated OTS diodes shows that the OTS layer of the diodes remains unaffected by high temperature up to approximately 450 °C which is significant in thermal energy harvesting applications, where the diode may be exposed to high temperatures
High-Performance Atomic Layer Deposited Al2O3 Insulator Based Metal-Insulator-Metal Diode
No full textThe fabrication of metal–insulator– metal (MIM) diode using an ultrathin Al2O3 insulator layer, deposited using atomic layer deposition (ALD) is presented. The Al2O3 insulating layer was found to be highly uniform throughout the diode junction, effectively overcoming the main fabrication challenge in MIM diodes. The diodes exhibit strong non-linear current–voltage curves, have a typical zero-bias curvature coefficient of 5.4 V−1 and a zero-bias resistance of approximately 118 kΩ, a value considerably smaller than other MIM diode topologies and that allows more current to be rectified. Other results including current ratio and yield of the diode also competes favorably with the state-of-the-art MIM diodes such as the recently produced metal-octadecyltrichlorosilane (OTS)-metal structure
Factors influencing job loss and early retirement in working men with prostate cancer—findings from the population-based Life After Prostate Cancer Diagnosis (LAPCD) study
No full textPurpose: To investigate factors associated with job loss and early retirement in men diagnosed with prostate cancer (PCa) 18–42 months previously. Methods: Men ≤ 60 years at diagnosis who completed the Life After Prostate Cancer Diagnosis (LAPCD) survey were identified. Men who moved from employment at diagnosis to unemployment (EtoU) or retirement (EtoR) at survey (18–42 months post-diagnosis) were compared to men remaining in employment (EtoE). Sociodemographic, clinical and patient-reported factors were analysed in univariable and multivariable analysis. Results: There were 3218 men (81.4%) in the EtoE, 245 (6.2%) in EtoU and 450 (11.4%) in the EtoR groups. Men with stage IV disease (OR = 4.7 95% CI 3.1–7.0, relative to stage I/II) and reporting moderate/big bowel (OR = 2.5, 95% CI 1.6–3.9) or urinary problems (OR = 2.0, 95% CI 1.4–3.0) had greater odds of becoming unemployed. Other clinical (≥ 1 comorbidities, symptomatic at diagnosis) and sociodemographic (higher deprivation, divorced/separated), living in Scotland or Northern Ireland (NI)) factors were predictors of becoming unemployed. Men who were older, from NI, with stage IV disease and with caring responsibilities had greater odds of retiring early. Self-employed and non-white men had lesser odds of retiring early. Conclusion: PCa survivors who retire early following diagnosis do not report worse urinary or bowel problems compared to men remaining in employment. However, we identified clinical and sociodemographic factors which increased unemployment risk in PCa survivors. Implications for Cancer Survivors: Targeted support and engagement with PCa survivors at risk of unemployment, including their families and employers, is needed.</p
Enhanced narrow-band operation of ultra-fast rectennas
No full textAn effective impedance matching technique for rectennas (an antenna coupled with rectifier) operating at specific frequencies is presented. The rectifier consists of a MIM junction with a molecular insulator. The method used two coplanar strip lines emerging from the antenna feed-point, to correct for the reactive component of the antenna impedance on one side, and to connect the rectifier and transform its impedance on the other side. Microwave and mm-wave characterization of the devices showed that the output voltage of the impedance matched rectenna is almost an order of magnitude higher than that of a control device without matching network at 20 GHz
Metal-insulator-metal diodes fabricated on flexible substrates
No full textThe fabrication and testing of metal-insulator-metal (MIM) diodes on a flexible substrate for microwave and mm-wave applications are presented. The diodes utilized octadecyltrichlorosilane (OTS), which self assembles to form a thin, pin holes free insulator. Preliminary electrical analysis shows that the diodes have a typical zero bias resistance of approximately 80 kΩ, zero-bias curvature coefficient (γ_ZB) of approximately 5.5 V-1, and voltage responsivity of 3.1 kV/W at a frequency of 1 GHz, and are produced with over 90% device yield. The fabrication process is simple and cost effective, environmentally friendly, and demonstrates the possibility of roll-to-roll volume manufacturing of MIM diodes
Impedance matching at THz frequencies: Optimizing power transfer in rectennas
No full textA simple and elegant method for matching the impedance of a typical THz self-complementary bowtie antenna to the high-impedance of a nanodiode is proposed. Two twin-lead balanced lines emerging from the antenna feed-point are used to connect the diode, correct for the reactive component of the antenna impedance and compensate the parasitic capacitance of the diode. Numerical simulations considering a model rectenna with a metal-insulator-metal diode showed that impedances up to several kΩ can be effectively matched
