Spinel, an overlooked crystalline phase of Igzo

In the family of semiconducting oxides, InGaZnO4 (IGZO) is most attractive due to the absence of mobile holes and the preservation of a relative high electron mobility when the material is in the amorphous phase. Especially this last characteristic enables low deposition temperature (Td), beneficial for the application as semiconducting channels of thin film transistors (TFT) in optical displays and 3D memory elements. However, a disadvantage related to the amorphous phase is the distribution of bonding energies of oxygen anions, which is directly related to the distributed distances with respect to the neighboring metal cations [1], leading to free electron formation readily at low temperature. Please click Download on the upper right corner to see the full abstract

Pulsed chemical vapor deposition of conformal GeSe for application as an OTS selector

The ovonic threshold switch (OTS) selector based on the voltage snapback of amorphous chalcogenides has received tremendous attention as it provides several desirable characteristics such as bidirectional switching, a controllable threshold voltage, high drive currents, and low leakage currents. GeSe is a well-known OTS selector that fulfills all the requirements imposed by future high-density storage class memories. Here, we report on pulsed chemical vapor deposition (CVD) of amorphous GeSe by using GeCl2 center dot C4H8O2 as a Ge source and two different Se sources namely bis-trimethylsilylselenide ((CH3)(3)Si)(2)Se (TMS)(2)Se and bis-triethylsilylselenide ((C2H5)(3)Si)(2)Se (TES)(2)Se. We utilized total reflection X-ray fluorescence (TXRF) to study the kinetics of precursor adsorption on the Si substrate. GeCl2 center dot C4H8O2 precursor adsorption on a 300 mm Si substrate showed under-dosing due to limited precursor supply. On the other hand, the Se precursor adsorption is limited by low reaction efficiency as we learned from a better within-wafer uniformity. Se precursors need Cl sites (from Ge precursor) for precursor ligand exchange reactions. Adsorption of (TMS)(2)Se is found to be much faster than (TES)(2)Se on a precoated GeClx layer. Atomic layer deposition (ALD) tests with GeCl2 center dot C4H8O2 and (TMS)(2)Se revealed that the growth per cycle (GPC) decreases with the introduction of purge steps in the ALD cycle, whereas a higher GPC is obtained in pulsed-CVD mode without purges. Based on this basic understanding of the process, we developed a pulsed CVD growth recipe (GPC = 0.3 angstrom per cycle) of GeSe using GeCl2 center dot C4H8O2 and (TMS)(2)Se at a reactor temperature of 70 degrees C. The 20 nm GeSe layer is amorphous and stoichiometric with traces of chlorine and carbon impurities. The film has a roughness of similar to 0.3 nm and it starts to crystallize at a temperature of similar to 370 degrees C. GeSe grown on 3D test structures showed excellent film conformality

Impact of relaxation on the performance of GeSe true random number generator based on Ovonic threshold switching

Volatile Ovonic threshold switching (OTS) are promising not only as the selector in crossbar resistive switching memory arrays, but also as true random number generators (TRNG) by utilizing its probabilistic switching characteristics. However, investigation on the reliability of OTS-based TRNG is still lacking, which hinders its practical application. Previously, we found that switching probability is dependent on the pulse amplitude and width. In this work, we report that relaxation which happens during the time interval between pulses can cause switching probability drift. Optimizing the bit-generation waveform and modulating the pulse conditions could provide a practical solution, in addition to the impact of external bias and temperature. This work provides useful guidance for the practical design and operation of OTS-based TRNGs

New Insights of the Switching Process in GeAsTe Ovonic Threshold Switching (OTS) Selectors

Experimental evidence and analysis in this work provide new insights into the fast switching process in GeAsTe ovonic threshold switching (OTS) selectors. For the first time, the full switching-OFF process, covering the defect cluster shrinking and rupture stages, can be measured and characterized. Two distinct switch-OFF mechanisms and their dependence on the total impedance of the selector and resistor (1S1Rs) circuit are identified. The impact of series resistance value on the switching process, the 1S1Rs operation, and the underlying mechanisms can be explained by the dynamic resistance of OTS that is induced by the transition of defect clusters. This research sheds new light on OTS switching mechanism and its impact on 1S1Rs operation

Acromegaly

Acromegaly is an acquired disorder related to excessive production of growth hormone (GH) and characterized by progressive somatic disfigurement (mainly involving the face and extremities) and systemic manifestations. The prevalence is estimated at 1:140,000–250,000. It is most often diagnosed in middle-aged adults (average age 40 years, men and women equally affected). Due to insidious onset and slow progression, acromegaly is often diagnosed four to more than ten years after its onset. The main clinical features are broadened extremities (hands and feet), widened thickened and stubby fingers, and thickened soft tissue. The facial aspect is characteristic and includes a widened and thickened nose, prominent cheekbones, forehead bulges, thick lips and marked facial lines. The forehead and overlying skin is thickened, sometimes leading to frontal bossing. There is a tendency towards mandibular overgrowth with prognathism, maxillary widening, tooth separation and jaw malocclusion. The disease also has rheumatologic, cardiovascular, respiratory and metabolic consequences which determine its prognosis. In the majority of cases, acromegaly is related to a pituitary adenoma, either purely GH-secreting (60%) or mixed. In very rare cases, acromegaly is due to ectopic secretion of growth-hormone-releasing hormone (GHRH) responsible for pituitary hyperplasia. The clinical diagnosis is confirmed biochemically by an increased serum GH concentration following an oral glucose tolerance test (OGTT) and by detection of increased levels of insulin-like growth factor-I (IGF-I). Assessment of tumor volume and extension is based on imaging studies. Echocardiography and sleep apnea testing are used to determine the clinical impact of acromegaly. Treatment is aimed at correcting (or preventing) tumor compression by excising the disease-causing lesion, and at reducing GH and IGF-I levels to normal values. Transsphenoidal surgery is often the first-line treatment. When surgery fails to correct GH/IGF-I hypersecretion, medical treatment with somatostatin analogs and/or radiotherapy can be used. The GH antagonist (pegvisomant) is used in patients that are resistant to somatostatin analogs. Adequate hormonal disease control is achieved in most cases, allowing a life expectancy similar to that of the general population. However, even if patients are cured or well-controlled, sequelae (joint pain, deformities and altered quality of life) often remain

Charles De Koninck, Tout homme est mon prochain

Delhougne Henri. Charles De Koninck, Tout homme est mon prochain. In: Revue Philosophique de Louvain. Troisième série, tome 65, n°88, 1967. pp. 576-577

Pierre Husser, «Vieilles béquilles théologiques» ou science ?

Delhougne Henri. Pierre Husser, «Vieilles béquilles théologiques» ou science ?. In: Revue Philosophique de Louvain. Troisième série, tome 65, n°88, 1967. pp. 577-578