Low substrate temperature deposition of amorphous and microcrystalline silicon films on plastic substrates by hot-wire chemical vapor deposition

Amorphous and microcrystalline silicon films were deposited by radio-frequency plasma enhanced chemical vapor deposition (rf-PECVD) and hot-wire chemical Vapor deposition (HW-CVD) on plastic (polyethylene terephthalate-PET) at 100 degrees C and 25 degrees C. Structural properties of these films were measured by Raman spectroscopy. Electronic properties were measured by dark conductivity and photoconductivity. For amorphous silicon films deposited by rf-PECVD on PET, photosensitivities > 10(5) were obtained at both 100 degrees C and 25 degrees C, For amorphous silicon films deposited by HW-CVD, a photosensitivity of > 10(5) was obtained at 100 degrees C. Microcrystalline silicon films deposited by HW-CVD at 95% hydrogen dilution had sigma(ph) similar to 10(-4) Omega(-1) cm(-1), while maintaining a photosensitivity of similar to 10(2) at both 100 degrees C and 15 degrees C. Microcrystalline silicon films with a large crystalline fraction (>50%) can be deposited by HW-CVD all the way down to room temperature. All the films had good adhesion and mechanical stability as neither adhesive nor cohesive failure was observed even when the substrates were bent elastically.Fundação para a Ciência e Tecnologia (FCT) Universidade do Minho (UM) Fundação Luso-Americana para o Desenvolvimento (FLAD

Doping of amorphous and microcrystalline silicon films deposited at low substrate temperatures by hot-wire chemical vapor deposition

The gas phase doping of amorphous (alpha -Si:H) and microcrystalline (muc-Si:H) silicon thin films deposited at substrate temperatures of 25 degreesC and 100 degreesC by hot-wire chemical vapor deposition is studied. Phosphine was used for n-type doping and diborane for p-type doping. The electronic and structural properties of the doped films are studied as functions of hydrogen dilution. Films were deposited on glass and polyethylene terephthalate. Similar dark conductivities, sigma (d), were obtained for the doped films deposited on either substrate. sigma (d) above 10(-6) Omega (-1) cm(-1) were obtained for a-Si:H films doped n-type at 25 degreesC and 100 degreesC (sigma (d)> 10(-4) Omega (-1) cm(-1)) and for alpha -Si:H doped p-type only at 100 degreesC. sigma (d), equal or above 10(-1) Omega (-1) cm(-1), were obtained for muc-Si:H doped p-type at 25 degreesC and 100 degreesC for Ac-Si:H doped n-type. only at 100 degreesC. Isochronal annealing at temperatures up to 200 degreesC reveals that, while the dopants are fully activated in microcrystalline samples, they are only partially activated in amorphous films deposited at a low substrate temperature.Fundação para a Ciência e Tecnologia (FCT) University of Minho (UM

Electronic and structural properties of doped amorphous and nanocrystalline silicon deposited at low substrate temperatures by radio-frequency plasma-enhanced chemical vapor deposition

The gas phase doping of hydrogenated amorphous silicon and hydrogenated nanocrystalline silicon thin films deposited on glass and on plastic (polyethylene terephthalate) substrates is reported. Two substrate temperatures were used during deposition: 25 degreesC and 100 degreesC. Films were deposited by radio-frequency plasma-enhanced chemical vapor deposition using phosphine or diborane for n- or p-type doping, respectively. Similar electronic and structural properties are obtained for the doped films deposited on either substrate. Hydrogen dilution of silane is used to improve the electronic and structural properties of the amorphous films and to obtain nanocrystalline films. The most conductive amorphous films have n-type dark conductivity at room temperature similar to10(-3) Omega(-1) cm(-1) and similar to10(-5) Omega(-1) cm(-1) when deposited at 100degreesC and 25degreesC, respectively, or p-type room-temperature dark conductivity similar to10(-7) Omega(-1) cm(-1) at both substrate temperatures. The most conductive nanocrystalline films deposited at 100 degreesC have n- and p-type dark conductivity at room temperature above 10(-2) Omega(-1) cm(-1) while nanocrystalline films deposited at 25 degreesC only have p-type conductivity higher than 10(-2) Omega(-1) cm(-1) at room temperature. Isochronal annealing at temperatures up to 300 degreesC showed that the dopants are fully activated at the deposition temperature in doped nanocrystalline samples and that they are only partially activated in amorphous films deposited at low substrate temperatures.Fundação para a Ciência e Tecnologia (FCT) Universidade do Minho (UM

Optimization of deposition parameters for thin silicon films on flexible substrates in a hot-wire chemical vapor deposition reactor

This paper studies the deposition of thin silicon films from silane on plastic substrates in a recently build hot-wire chemical vapor deposition reactor. Hydrogen dilution of silane was used to induce amorphous-to-nanocrystalline phase transition. Thin-film deposition rate, r(d), is roughly proportional to silane concentration during deposition but the proportionality factor depends on filament temperature, T-fil. At T-fil similar to 2500 degrees C (1900 degrees C), r(d) increases from 2.1 angstrom/s (1.2 angstrom/s) at 97% H-2 dilution to 14.5 angstrom/s (10.7 angstrom/s) for films deposited from pure silane. At T-fil similar to 2500 degrees C, films deposited under 80% H-2 dilution were amorphous, under 90% H-2 dilution the crystalline fraction was X-C = 49.4% and under 95% H-2 dilution, X-C = 52.8%. At T-fil similar to 1900 degrees C, samples were amorphous up to similar to 95% H-2 dilution where a crystalline fraction of 22.3% was measured. Films with amorphous structure have sigma(d) similar to 10(-10)-10(-9) Omega(-1.)cm(-1) while those with a measured crystalline fraction have sigma(d)similar to 10(-7)-10(-5) Omega(-1)cm(-1), depending on the amount of crystalline fraction and grain size. Films with lower sigma(d) have optical band gap in the range similar to 1.85-1.9 eV, typical of hydrogenated amorphous silicon, while those with higher sigma(d) have larger optical band gap (similar to 2 eV), typical of hydrogenated nanocrystalline silicon. Adhesion of the films to the plastic substrate was good, as they survived bending to small radius of curvature (< 1 mm) without peeling. Structural, optical and transport properties were similar on films deposited both on PEN and on glass under the same deposition conditions.Fundação para a Ciência e a Tecnologia (FCT

Electronic transport in low-temperature silicon nitride

Perpendicular current transport through thin silicon nitride films deposited at 100 degreesC by radio frequency chemical vapor deposition (RF) is measured between patterned square contacts with side lengths between 5 and 200 mum. Hydrogen dilution, silane-to-ammonia ratio, and total gas flow were varied to achieve control of film properties. The dependence of the current on the applied field and measurement temperature are correlated to structural parameters such as the index of refraction, etching rate in buffered hydrofluoric acid and infrared vibrational band strengths. Using the appropriate deposition parameters, it is possible to prepare, at 100 degreesC, silicon nitride dielectric films with electronic properties compatible with use as gate dielectrics of thin-film transistors.Fundação para a Ciência e Tecnologia (FCT) Universidade do Minho (UM

The Role of Hyperbaric Oxygen Therapy in Pneumatosis Cystoides Intestinalis—A Scoping Review

Pneumatosis cystoides intestinalis (PCI) is characterized by gas-filled cysts within gastrointestinal tract wall from esophagus to rectum, with preferential involvement of large and small intestine. PCI is rare with an estimated incidence of 0.03 to 0-2% in general population. PCI can be distinguished into idiopathic (15%) or secondary (85%) and the clinical picture ranges from completely asymptomatic to life-threatening intraabdominal complications. Although etiology of PCI appears to be multifactorial, the exact pathophysiology is poorly understood and two main theories have been proposed (mechanical and bacterial). Over the last decades, an enormous therapeutic armamentarium was considered in PCI's management, including hyperbaric oxygen therapy (HBOT). Treatment comprises conservative treatment in mild cases to surgery in highly symptomatic and complicated PCI. In the late 70s, HBOT started to be used in selected cases of PCI not responding to conservative measures. Since then, several case reports, case series, and reviews have been published in the literature with variable outcomes. The overall response rate and complete response were 92.1% (n = 82/89) and 65.2% (n = 58/89), respectively, with a median follow-up of 7 months. Furthermore, HBOT is extremely safe, with few reported complications in the literature when used for PCI. Nevertheless, a randomized, controlled, and double-blind clinical trial is unlikely to occur given the rarity of PCI, logistical issues of HBOT, and methodological considerations related to adequate blinding with a sham-controlled group. HBOT in combination with personalized diet and antibiotics may be beneficial for moderate to severe PCI in patients with no indication for emergency exploratory laparotomy. The purpose of this article is to synthesize the existing data, analyse results of previous studies, identify gaps in knowledge, and discuss PCI' management, including the proposal of an algorithm, with a special focus on HBOT.info:eu-repo/semantics/publishedVersio

Next-Generation Sequencing in Breast Cancer Management: A Case Report of Genomic Tumour Evolution over Time

The clinicopathological breast cancer subtypes are used in clinical practice to better anticipate biological behaviour and guide systemic treatment strategy. In the adjuvant setting, genomic assay recurrence scores became widely available for luminal-like disease. Recently, next-generation sequencing (NGS) platforms have been used, essentially, in more advanced disease setting, in situations refractory to conventional treatment, or even in rare cancers for which there are no established treatment guidelines. Moreover, subpopulations of cancer cells with unique genomes within the same patient may exist across different regions of a tumour or evolve over time, which is called intratumoural heterogeneity. We herein report a case of a 38-year-old woman with breast cancer whose primary and metastatic disease exhibited discordant expression of hormone receptors, with the former being positive and the latter negative. Furthermore, the NGS analysis revealed slight and dynamic changes of mutational profiles between different metastatic lesions, potentially impacting breast cancer management and prognosis. These alterations may reflect tissular and temporal changes in tumour subclones and may also be due to the selective pressure caused by antineoplastic treatment. The use of genomic analyses in order to improve cancer treatment has been studied prospectively with encouraging results. The widespread use of NGS tests in clinical practice also creates new challenges. The most relevant may be to know which genomic alterations detected should be valued and how they should be targeted.info:eu-repo/semantics/publishedVersio

Right Cardiac Intracavitary Metastases from a Primary Intracranial Myxofibrosarcoma

Primary intracranial myxofibrosarcoma is exceedingly rare, with less than 10 cases published. We present a case of a 23-year-old man with previous history of a primary low grade myxofibrosarcoma of the left parietal-occipital convexity resected in March 1999. He subsequently underwent several interventions for multiple local recurrent disease until March 2004. At that time, complete remission was documented. About 8 years later, in February 2012, the patient was admitted to the emergency room with refractory acute pulmonary oedema. On work up, sustained monomorphic ventricular tachycardia and hyperechoic myocardial mass with invasion of the right ventricular cavity were detected. Electrical cardioversion was unsuccessful and irreversible cardiac arrest followed. The autopsy confirmed multiple bilateral lung metastases, malignant pulmonary embolism and myocardial invasion by the primary tumour, with intracavitary cardiac thrombosis and absence of intracranial disease. To the best of our knowledge, this is the first report of extracranial metastases of this neoplasm.info:eu-repo/semantics/publishedVersio

Silicon nanowire arrays coupled with cobalt phosphide spheres as low-cost photocathodes for efficient solar hydrogen evolution

We demonstrate the first example of silicon nanowire array photocathodes coupled with hollow spheres of the emerging earth-abundant cobalt phosphide catalysts. Compared to bare silicon nanowire arrays, the hybrid electrodes exhibit significantly improved photoelectrochemical performance toward the solar-driven H2 evolution reaction.L. F. Liu acknowledges the financial support by the FCT Investigator grant (IF/01595/2014)

Piezoresistor sensor fabrication by direct laser writing on hydrogenated amorphous silicon

In this paper we report on the 532 nm Nd:YAG laser-induced crystallization of 10 nm thick boron-doped hydrogenated amorphous silicon thin films deposited on flexible polyimide and on rigid oxidized silicon wafers by hot-wire chemical vapor deposition. The dark conductivity increased from ~10-7 -1cm-1, in the as-deposited films, to ~10 and 50 -1cm-1 after laser irradiation, on rigid and flexible substrates, respectively. Depending on type of substrate, laser power and fluence, a Raman crystalline fraction between 55 and 90% was measured in HWCVD films, which was higher than observed in rf-PECVD films (35 - 55%). Crystallite size remained small in all cases, in the range 6-8 nm. Due to a very high conductivity contrast (>7 orders of magnitude) between amorphous and crystallized regions, it was possible to define conductive paths in the a-Si:H matrix, by mounting the sample on a X-Y software-controlled movable stage under the laser beam, with no need for the usual lithography steps. The resistors scribed by direct laser writing had piezoresistive properties, with positive gauge factor ~1. The details of the laser interaction process with the Si film were revealed by scanning electron microscopy imaging.(undefined