Temperature Dependent Current-voltage Characteristics of P-type Crystalline Silicon Solar Cells Fabricated Using Screen-printing Process

We have fabricated p-type crystalline silicon (Si) solar cells using screen-printing process and investigated their electrical properties. Ph screen printing process led to the uniform formation of n+ emitter. As a result of interaction between Ph-dopant paste and Si substrate, a phosphosilicate glass layer was formed on n+ emitter surface. The current-voltage characteristics were carried out in the temperature range of 175 – 450 K in steps of 25 K. The variation in current level at a particular voltage strongly depended on temperature, indicating that the current transport across the junction was a temperature activated process. The reverse leakage current gradually increased with increasing measurement temperature up to 350 K, above which it rapidly increased. Arrhenius plot of the leakage current revealed that reverse leakage current in low and high temperature regions were dominated by the tunneling mechanism, and generation and recombination mechanism, respectively. Keywords: P-type Si solar cell, screen-printing, I-V, tunneling, generation and recombination, reverse leakage curren

Surface passivation of semiconducting oxides by self-assembled nanoparticles

Physiochemical interactions which occur at the surfaces of oxide materials can significantly impair their performance in many device applications. As a result, surface passivation of oxide materials has been attempted via several deposition methods and with a number of different inert materials. Here, we demonstrate a novel approach to passivate the surface of a versatile semiconducting oxide, zinc oxide (ZnO), evoking a self-assembly methodology. This is achieved via thermodynamic phase transformation, to passivate the surface of ZnO thin films with BeO nanoparticles. Our unique approach involves the use of BexZn1-xO (BZO) alloy as a starting material that ultimately yields the required coverage of secondary phase BeO nanoparticles, and prevents thermally-induced lattice dissociation and defect-mediated chemisorption, which are undesirable features observed at the surface of undoped ZnO. This approach to surface passivation will allow the use of semiconducting oxides in a variety of different electronic applications, while maintaining the inherent properties of the materials

Safety and efficacy study of laparoscopic or robotic radical surgery using an endoscopic stapler for inhibiting tumour spillage of cervical malignant neoplasms evaluating survival (SOLUTION): a multi-centre, open-label, single-arm, phase II trial protocol

The Laparoscopic Approach to Cervical Cancer trial and Surveillance, Epidemiology, and End Results program database study demonstrated that minimally invasive radical hysterectomy was inferior to abdominal radical hysterectomy in terms of disease recurrence and survival. Among risk factors related to poor prognosis after minimally invasive surgery (MIS), tumour spillage during intracorporeal colpotomy became a significant issue. Thus, we designed this trial to evaluate the efficacy and safety of minimally invasive radical hysterectomy using an endoscopic stapler for early-stage cervical cancer. This trial is a prospective, multi-centre, open-label, single-arm, non-inferiority phase II study. The nine organisations will participate in this trial after the approval of the institutional review board. Major eligibility criteria include women aged 20 years or older with cervical cancer stage IB1 squamous cell carcinoma, adenocarcinoma, or adenosquamous carcinoma according to the revised 2009 FIGO staging system who will undergo type B2 or C hysterectomy by MIS. The primary endpoint is the 4.5-year disease-free survival (DFS) rate between abdominal radical hysterectomy and MIS using an endoscopic stapler. For calculating the sample size, we hypothesised that the 4.5-year DFS rate after MIS using an endoscopic stapler is assumed to be the same after abdominal radical hysterectomy at 90.9%, and the non-inferiority margin was 7.2%. When we consider a three-year accrual and 4.5-year follow-up, at least 13 events must happen, requiring a total of 111 patients assuming a statistical power of 80% and the one-tailed test of 5% significance. A total of 124 patients is needed, considering a drop-out rate of 10%. We expect intracorporeal colpotomy using an endoscopic stapler may prevent tumour spillage during MIS for stage IB1 cervical cancer, showing a comparable prognosis with abdominal radical surgery.This study was supported by Johnson & Johnson. The funder has no role in study design, writing of the manuscript and the decision to submit the report for publication

Electrical and microstructural properties of low-resistance Ti/Re/Au ohmic contacts to n-type GaN

The microstructural and electrical properties of Ti/Re/Au (10 nm/10 nm/50 nm) ohmic contacts to moderately doped n-type GaN (4.0 × 1018 cm–3) have been investigated by current–voltage (I –V), Auger electron microscopy (AES) and transmission electron microscopy (TEM). The electrical characteristics of as-deposited and annealing at temperatures below 800 °C samples exhibit non-linear behaviour. However, the sample showed ohmic behaviour when the contact is annealed at 900 °C for 1 min in nitrogen ambient. The Ti/Re/Au contacts give specific contact resistance as low as 8.6 × 10–6 Ω cm2 after annealing at 900 °C. It is shown that the surface of the as-deposited contact is fairly smooth and slightly degraded when the contact is annealed at 900 °C. The Ti/Re/Au ohmic contact showed good edge acuity after annealing at 900 °C for 1 min. Based on the Auger electron microscopy and transmission electron microscopy results, possible ohmic formation mechanisms for the Ti/Re/Au contacts to the n-type GaN are described and discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Electrical and structural properties of low-resistance Pt/Ag/Au ohmic contacts to p-type GaN

A Pt (20nm)/Ag (50nm)/Au (30nm) metallization scheme has been investigated for producing low-resistance ohmic contacts to moderately doped p-type GaN (1.3×1017cm−3). It is shown that the as-deposited contacts exhibit a linear I–V characteristic with a specific contact resistance of 4.43×10−3Ωcm2. The Pt/Ag/Au contact produced a specific contact resistance as low as 1.70×10−4Ωcm2 after annealing at 800°C for 1min in a N2 atmosphere. It is further shown that the surface morphology of the contact annealed at 800°C (RMS roughness of 19.9nm) became somewhat degraded compared with that of the as-deposited one (RMS roughness of 3.3nm). Based on the Auger electron microscopy and X-ray diffraction results, possible explanations for the improvement of the ohmic behavior are described

Microstructural properties of thermally stable Ti/W/Au ohmic contacts on n-type GaN

We have investigated the microstructural and electrical characteristics of Ti/W/Au ohmic contacts on n-type GaN (4.0×1018cm−3) using Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) after annealing at 900°C. It is shown that the electrical properties are improved upon annealing at 900°C for 1min in nitrogen ambient. The 900°C annealed contact produced a specific contact resistance of 8.4×10−6Ωcm2. It is further shown that the contact exhibits thermal stability during annealing at 900°C. Based on the Auger electron microscopy and transmission electron microscopy studies, the formation of TiN layer results in an excess of N vacancies near the surface of the GaN layer, which could be the reason for the low-resistance of the Ti/W/Au contact

The effect of annealing temperature on electrical and structural properties of Rh/Au Schottky contacts to n-type GaN

The effect of thermal annealing temperature on electrical and structural properties of Rh/Au Schottky contacts to n-type GaN (∼4 × 1017 cm−3) has been investigated by current–voltage (I–V), capacitance–voltage (C–V), x-ray diffraction (XRD) and Auger electron microscopy (AES). Calculations showed that the Schottky barrier height of the as-deposited Rh/Au contact was 0.57 eV (I–V) and 0.62 eV (C–V), respectively. However, the Schottky barrier height increased with annealing temperature up to 500 °C, reaching maximum values of 0.84 eV (I–V) and 1.05 eV (C–V). Based on the Auger electron microscopy and x-ray diffraction results, the formation of gallide phases at the Rh/Au/n-GaN interface could be the reason for the increase of Schottky barrier heights after annealing at temperatures 400 °C and 500 °C

Structural and electrical properties of Mo/n-GaN schottky diodes

Abstract The electrical and structural properties of molybdenum (Mo) Schottky contact to n-type GaN (4.07 × 1018 cm–3) have been investigated before and after annealing at 600 °C. Measurements show that the Schottky barrier height of the as-deposited sample was 0.81 eV (I–V) and 1.02 eV (C–V), respectively. It is shown that when the sample is annealed at 400 °C the Schottky barrier height slightly decreases to 0.74 eV (I–V) and 0.92 eV (C–V), respectively. However, the barrier height degraded to 0.56 and 0.73 eV when the sample was annealed at 600 °C for 1 min in nitrogen ambient. Based on the Auger electron microscopy and X-ray diffraction results, the formation of nitride phases at the Mo/n-GaN interface could be the reason for degradation of Schottky barrier height upon annealing at 600 °C. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim