Novel type of whisker-tip cantilever based on GaN microrods for atomic force microscopy.

High-resolution scanning probe microscopy (SPM) is a fundamental and efficient technology for surface characterization of modern materials at the subnanometre scale. The bottleneck of SPM is the probe and scanning tip. Materials with stable electrical, thermal, and mechanical properties for high-aspect-ratio (AR) tips are continuously being developed to improve their accuracy. Among these, GaN is emerging as a significant contender that serves as a replacement for standard Si probes. In this paper, for the first time, we present an approach that demonstrates the application of GaN microrods (MRs) as high-AR SPM probes. GaN MRs were grown using molecular beam epitaxy, transferred and mounted on a cantilever using focused electron beam-induced deposition and milled in a whisker tip using a focused ion beam in a scanning electron/ion microscope. The presence of a native oxide layer covering the GaN MR surface was confirmed by X-ray photoelectron spectroscopy. Current-voltage map measurements are also presented to indicate the elimination of the native oxide layer from the tip surface. The utility of the designed probes was tested using conductive atomic force microscopy and a 24-hour durability test in contact mode atomic force microscopy. Subsequently, the graphene stacks were imaged.

Influence of B/N co-doping on electrical and photoluminescence properties of CVD grown homoepitaxial diamond films.

Boron doped diamond (BDD) has great potential in electrical, and electrochemical sensing applications. The growth parameters, substrates, and synthesis method play a vital role in the preparation of semiconducting BDD to metallic BDD. Doping of other elements along with boron (B) into diamond demonstrated improved efficacy of B doping and exceptional properties. In the present study, B and nitrogen (N) co-doped diamond has been synthesized on single crystalline diamond (SCD) IIa and SCD Ib substrates in a microwave plasma-assisted chemical vapor deposition process. The B/N co-doping into CVD diamond has been conducted at constant N flow of N/C âˆ¼ 0.02 with three different B/C doping concentrations of B/C âˆ¼ 2500 ppm, 5000 ppm, 7500 ppm. Atomic force microscopy topography depicted the flat and smooth surface with low surface roughness for low B doping, whereas surface features like hillock structures and un-epitaxial diamond crystals with high surface roughness were observed for high B doping concentrations. KPFM measurements revealed that the work function (4.74-4.94 eV) has not varied significantly for CVD diamond synthesized with different B/C concentrations. Raman spectroscopy measurements described the growth of high-quality diamond and photoluminescence studies revealed the formation of high-density nitrogen-vacancy centers in CVD diamond layers. X-ray photoelectron spectroscopy results confirmed the successful B doping and the increase in N doping with B doping concentration. The room temperature electrical resistance measurements of CVD diamond layers (B/C âˆ¼ 7500 ppm) have shown the low resistance value âˆ¼9.29 Ω for CVD diamond/SCD IIa, and the resistance value âˆ¼16.55 Ω for CVD diamond/SCD Ib samples.

Layer number dependence of the work function and optical properties of single and few layers MoS2: effect of substrate.

We have examined the influence of flake-substrate effects that affect one and few layers of MoS2 in terms of their electrical and optical properties. In the measurements, we used SiO2/Si substrates with etched cavities and aluminum electrodes. Suspended areas are easily identifiable both on images depicting the topography and on the surface potential maps measured with the Kelvin probe force microscopy. Compared to the SiO2/Si supported material, surface potential decrease is observable at the membrane. The surface potential value of the flakes located on the electrodes is the lowest. PL measurements prove that single MoS2 monolayer was obtained. Suspended regions are also correlated with maps obtained as a result of Raman spectroscopy.

Clinical evaluation of C-reactive protein and procalcitonin for the early detection of postoperative complications after laparoscopic sleeve gastrectomy.

INTRODUCTION: Among the most common early complications after bariatric surgery are anastomosis leak and bleeding. In order to react quickly and perform accurate treatment before the clinical signs appear, early predictors should be found. In the study C-reactive protein (CRP) and procalcitonin (PCT) levels were investigated. Characterized by a relatively short half-life, they can predict surgical complications. AIM: To develop and implement certain standards for early detection of complications. MATERIAL AND METHODS: The study involved 319 adults who underwent laparoscopic sleeve gastrectomy (LSG) as a surgical intervention for morbid obesity at the Department of General Surgery of Ceynowa Hospital in Wejherowo. Every patient had CRP and PCT levels measured before the surgery and on the 1st and 2nd postoperative day (POD). RESULTS: Early postoperative complications occurred in 19 (5.96%) patients. Septic and non-septic complications occurred in 3 and 16 patients respectively. Among the patients with septic postoperative complications CRP level increased significantly on the 2nd POD compared to the remainder (p = 0.0221). Among the patients with non-septic postoperative complications CRP level increased significantly on the 1st and 2nd POD compared to the remainder. Among the patients with septic and non-septic postoperative complications PCT level increased significantly on the 2nd POD compared to the remainder. CONCLUSIONS: The CRP and PCT level are supposed to be relevant diagnostic markers to predict non-septic and septic complications after LSG.

Scanning probe microscopy investigations of the electrical properties of chemical vapor deposited graphene grown on a 6H-SiC substrate.

Sublimated graphene grown on SiC is an attractive material for scientific investigations. Nevertheless the self limiting process on the Si face and its sensitivity to the surface quality of the SiC substrates may be unfavourable for later microelectronic processes. On the other hand, chemical vapor deposited (CVD) graphene does not posses such disadvantages, so further experimental investigation is needed. In this paper CVD grown graphene on 6H-SiC (0001) substrate was investigated using scanning probe microscopy (SPM). Electrical properties of graphene were characterized with the use of: scanning tunnelling microscopy, conductive atomic force microscopy (C-AFM) with locally performed C-AFM current-voltage measurements and Kelvin probe force microscopy (KPFM). Based on the contact potential difference data from the KPFM measurements, the work function of graphene was estimated. We observed conductance variations not only on structural edges, existing surface corrugations or accidental bilayers, but also on a flat graphene surface.