Abraham Israel Calderón-Martínez

Zinc oxide is one of the prominent materials for optoelectronic applications. Chemical and physical growth methods strongly influence its properties, which can be tailored by incorporating suitable dopants. This work explores the electrical properties of Ga doped ZnO films grown by rf sputtering under photon excitation from a tungsten-halogen lamp. Experiments were performed under short and long transient illumination conditions. The characteristic times during light on/off cycles were determined. The fastest response was observed for undoped films, indicating that Ga introduces deep traps in the band gap, slowing photoresponse dynamics. Structural, optical and dark electrical properties were also analyzed as a function of Ga concentration and substrate temperature. Ga doping improved conductivity in all samples. Films grown at 300 ºC with 3 at.% showed the best conductivity. A correlation between the slope of infrared transmittance and free electron density was observed. Terahertz spectroscopy probed deep levels in the ZnO band gap, revealing an inverse correlation between conductivity and IR absorbance (0.11–0.99 eV). The work function was 4.46 eV for undoped ZnO and 4.61 eV for films with 5 at.% Ga.

Zinc oxide is one of the prominent materials for optoelectronic applications. Chemical and physical growth methods strongly influence its properties, which can be tailored by incorporating suitable dopants. This work explores the electrical properties of Ga doped ZnO films grown by rf sputtering under photon excitation from a tungsten-halogen lamp. Experiments were performed under short and long transient illumination conditions. The characteristic times during light on/off cycles were determined. The fastest response was observed for undoped films, indicating that Ga introduces deep traps in the band gap, slowing photoresponse dynamics. Structural, optical and dark electrical properties were also analyzed as a function of Ga concentration and substrate temperature. Ga doping improved conductivity in all samples. Films grown at 300 ºC with 3 at.% showed the best conductivity. A correlation between the slope of infrared transmittance and free electron density was observed. Terahertz spectroscopy probed deep levels in the ZnO band gap, revealing an inverse correlation between conductivity and IR absorbance (0.11–0.99 eV). The work function was 4.46 eV for undoped ZnO and 4.61 eV for films with 5 at.% Ga.

This work presents, for the first time, power generation using diabetic urine as fuel. The energy conversion is achieved through a paper-based microfluidic fuel cell. Urine has recently gained attention as a source of novel biomarkers for early disease detection, making the use of diabetic urine as fuel particularly relevant to the development of autonomous portable medical devices. A key challenge in using diabetic urine as fuel lies in the fact that it contains various molecules and compounds that can block or poison the fuel cell's electrodes. This study introduces a selective catalyst of ZnO and nickel-based particles that oxidize the urea in human urine. Different concentrations of Ni (3%, 6%, and 9%) were evaluated to optimize catalyst activity. The best performance of the diabetic urine-microfluidic fuel cell was achieved with the ZnO-Ni at 3%, yielding a maximum voltage of 0.89 V, a maximum current density of 1.18 mA cm−2, and a maximum power density of 1.26 mW cm−2. These results demonstrate the potential for enhancing point-of-care devices through paper-based microfluidic fuel cell stacks.