Modification of HF-treated silicon (100) surfaces by scanning tunneling microscopy in air under imaging conditions

The modification of HF-etched silicon (100) surface with a scanning tunneling microscope(STM) operated in air is studied for the first time in samples subjected to the standard HF etching without the follow-up rinsing in H2O. The modifications are produced in air under normal STM imaging conditions (V t =−1.4 V and I t =2 nA). The simultaneous acquisition of topographical, current image tunneling spectroscopy and local barrier-height images clearly shows that the nature of the modification is not only topographical but also chemical. The features produced with a resolution better than 25 nm are attributed to a tip-induced oxidation enhanced by the presence of fluorine on the surface

Advanced measurement techniques for the characterization of ReRAM devices

In some Resistive Random Access Memories (ReRAM), which could become the next generation of non-volatile memories [1], the voltage-controlled high and low resistance states (HRS and LRS, respectively) are associated to the creation (Set) and disruption (Reset) of a conductive filament (CF) that locally connects (LRS) or disconnects (HRS) the electrodes [2]. Usually, a current limit (CL) must be fixed during the Set process. Typically, these devices are characterized using source measurement units (SMU) to measure the current through the device. However, most of the SMU have a low sampling rate (around 1sample/1ms) and the current limitation mechanism used by the equipment is not well understood. To overcome these limitations, in this work, a low-cost setup with large sampling rate (larger than 1sample/10μs) is presented which, in addition, includes a well-controlled wide-range current limiting unit, CLCU (Fig. 1). The system is suitable to capture fast transients during the Set/Reset processes (Fig. 2) and to detect HRS Random Telegraph Noise (RTN) unresolvable by SMUs (Fig. 3) [3]. These device-level measurements can be combined with a Conductive Atomic Force Microscope, to get information on CF properties that cannot be directly measured at device level, as, for example, the spatial distribution of current in the CF at LRS and HRS (Fig. 4) [4]. Please click Additional Files below to see the full abstract

Degradation of polycrystalline HfO2-based gate dielectrics under nanoscale electrical stress

The evolution of the electrical properties of HfO2/SiO2/Si dielectric stacks under electrical stress has been investigated using atomic force microscope-based techniques. The current through the grain boundaries (GBs), which is found to be higher than thorough the grains, is correlated to a higher density of positively charged defects at the GBs. Electrical stress produces different degradation kinetics in the grains and GBs, with a much shorter time to breakdown in the latter, indicating that GBs facilitate dielectric breakdown in high-k gate stacks

Gaining insight into the Clinical Practice Guideline development processes: qualitative study in a workshop to implement the GRADE proposal in Spain

BACKGROUND: The GRADE method represents a new approach to grading the quality of evidence and strength of recommendations in the preparation of Clinical Practice Guidelines (CPG). In the context of a pilot study to assess the implementability of the system in Spain, we considered it relevant to gain an insight into the significance of the perceptions and attitudes expressed by the actual experts participating in the system try-out. METHODS: Qualitative research with an ethnographic approach, through non-participant observation and focus groups within the context of a consensus workshop in which 19 CPG experts participated to evaluate the GRADE proposal using 12 evidence tables taken from hypertension, asthma and arthritis CPGs. The interventions were recorded, under a guarantee of confidentiality. The transcriptions and field notes were analyzed, based on a sociological discourse analysis model, and the provisional findings were re-sent to participants in order to improve their validity. RESULTS: 1) Certain problems over procedure and terminology hindered the acceptance of this new method as a common reference system for the preparation of CPGs. 2). A greater closeness to clinical practice was accompanied by concerns over value judgments and subjectivity, with a demand for greater explicitness in the consensus process. 3). The type of "evidence" on which the guidelines are based, how and by whom the evidence is prepared, and what the role of the different actors should be, all constitute unresolved concerns in the CPG preparation and implementation processes. 4). The grading process is not neutral: professional background, prior experience and the degree of leadership all condition the participants' input and interactions. CONCLUSION: The findings obtained allow the quantitative evaluation to be better interpreted and, in turn, go beyond the particularities of the GRADE method. Adaptation to the complexities of clinical practice, the need for carefully designed multi-disciplinary work and the reflexivity present in the CPG preparation process, all represent lines of debate that are necessary to improve the CPG quality in the Spanish health care sector