The mechanisms responsible for the effects of consecutive irradiation and negative bias temperature (NBT) stress in p-channel power vertical double-diffused MOS (VDMOS) transistors are presented in ...this paper. The investigation was performed in order to clarify the mechanisms responsible for the effects of specific kind of stress in devices previously subjected to the other kind of stress. In addition, it may help in assessing the behaviour of devices subjected to simultaneous irradiation and NBT stressing. It is shown that irradiation of previously NBT stressed devices leads to additional build-up of oxide trapped charge and interface traps, while NBT stress effects in previously irradiated devices depend on gate bias applied during irradiation and on the total dose received. In the cases of low-dose irradiation or irradiation without gate bias, the subsequent NBT stress leads to slight further device degradation. On the other hand, in the cases of devices previously irradiated to high doses or with gate bias applied during irradiation, NBT stress may have a positive role, as it actually anneals a part of radiation-induced degradation.
The rise and fall of the Roman Empire was a socio-political process with enormous ramifications for human history. The Middle Danube was a crucial frontier and a crossroads for population and ...cultural movement. Here, we present genome-wide data from 136 Balkan individuals dated to the 1st millennium CE. Despite extensive militarization and cultural influence, we find little ancestry contribution from peoples of Italic descent. However, we trace a large-scale influx of people of Anatolian ancestry during the Imperial period. Between ∼250 and 550 CE, we detect migrants with ancestry from Central/Northern Europe and the Steppe, confirming that “barbarian” migrations were propelled by ethnically diverse confederations. Following the end of Roman control, we detect the large-scale arrival of individuals who were genetically similar to modern Eastern European Slavic-speaking populations, who contributed 30%–60% of the ancestry of Balkan people, representing one of the largest permanent demographic changes anywhere in Europe during the Migration Period.
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•A frontier region of ancient Rome was as cosmopolitan as the imperial center•Genetic proof that migrants identified as Goths were ethnically diverse confederations•Slavic-speaking migrants account for 30%–60% of the ancestry of Balkan peoples today•A model for integrating archaeology with genetics
Genome-wide data from 146 ancient Balkan individuals dating to the 1st millennium CE, together with detailed archaeological information, reveals internal migratory patterns during the Roman Empire and documents the demographic impact of Early Medieval Slavic migrations that significantly contributed to the present-day Balkan gene pool.
In this study, which is aimed at assessing a possible relationship between the recoverable and permanent components of negative bias temperature instability (NBTI) degradation, we investigate NBTI in ...commercial IRF9520 p-channel VDMOSFETs (vertical double diffused MOSFETs) stressed under particular pulsed bias conditions by varying the pulse on-time while keeping the off-time constant and vice versa. The stress-induced threshold voltage shifts are found to be practically independent of duty cycle when the pulse on-time is kept short or the off-time is kept long, and are found to start increasing with duty cycle only when the on-time is increased or the off-time is decreased beyond specific values. These results, which are discussed in terms of dynamic recovery effects and the mechanisms leading to NBTI degradation, point to the existence of an important correlation between the recoverable and permanent components of degradation.
In this study we investigate the dynamic recovery effects in IRF9520 commercial p-channel power vertical double diffused metal-oxide semiconductor field-effect transistors（VDMOSFETs） subjected to ...negative bias temperature（NBT）stressing under the particular pulsed bias. Particular values of the pulsed stress voltage frequency and duty cycle are chosen in order to analyze the recoverable and permanent components of stress-induced threshold voltage shift in detail. The results are discussed in terms of the mechanisms responsible for buildup of oxide charge and interface traps. The partial recovery during the low level of pulsed gate voltage is ascribed to the removal of recoverable component of degradation, i.e., to passivation/neutralization of shallow oxide traps that are not transformed into the deeper traps（permanent component）.Considering the value of characteristic time constant associated with complete removal of the recoverable component of degradation, it is shown that by selecting an appropriate combination of the frequency and duty cycle, the threshold voltage shifts induced under the pulsed negative bias temperature stress conditions can be significantly reduced, which may be utilized for improving the device lifetime in real application circuits.
Ancient DNA research in the past decade has revealed that European population structure changed dramatically in the prehistoric period (14,000-3000 years before present, YBP), reflecting the ...widespread introduction of Neolithic farmer and Bronze Age Steppe ancestries. However, little is known about how population structure changed from the historical period onward (3000 YBP - present). To address this, we collected whole genomes from 204 individuals from Europe and the Mediterranean, many of which are the first historical period genomes from their region (e.g. Armenia and France). We found that most regions show remarkable inter-individual heterogeneity. At least 7% of historical individuals carry ancestry uncommon in the region where they were sampled, some indicating cross-Mediterranean contacts. Despite this high level of mobility, overall population structure across western Eurasia is relatively stable through the historical period up to the present, mirroring geography. We show that, under standard population genetics models with local panmixia, the observed level of dispersal would lead to a collapse of population structure. Persistent population structure thus suggests a lower effective migration rate than indicated by the observed dispersal. We hypothesize that this phenomenon can be explained by extensive transient dispersal arising from drastically improved transportation networks and the Roman Empire's mobilization of people for trade, labor, and military. This work highlights the utility of ancient DNA in elucidating finer scale human population dynamics in recent history.
This paper shows some of the passenger difficulties when boarding trains. Overview of platform heights is discussed in accordance with international railway regulation. An overview of platform ...heights at Serbian railway lines and floor heights of passenger coaches, diesel units and electric multiple units for suburban and regional railway transport are shown. This paper is focused on the differences between procurement policy, regarding doorway compatibility with platforms, of diesel and electric multiple units for Serbian Railways and consequences of these acquisitions.
The effect of annealing on the recovery of electrically stressed power vertical double-diffused metal oxide semiconductor (VDMOS) transistors has been investigated. Behaviors of device threshold ...voltage and channel carrier mobility have been analyzed in terms of underlying changes in the densities of gate oxide charges and interface traps. The mechanisms responsible for the above-mentioned changes during the recovery of stressed devices have been analyzed as well. The annealing resulted in achieving stable threshold voltage and mobility, but did not ensure full recovery, as part of the stress-induced degradation remained permanent and could not be annealed. Namely, the annealing was found to enhance the neutralization of stress-induced oxide charges and the passivation of stress-induced interface traps, while the stability upon its completion resulted from the significantly decreased density of gate oxide charges and the possible balance between the processes of trap passivation and creation at the SiO2-Si interface.
The behaviour of oxide and interface defects in n-channel power vertical
double-diffused metal-oxide-semiconductor field-effect transistors, firstly
degraded by the gamma-irradiation and electric ...field and subsequently
recovered and annealed, is presented. By analyzing the transfer
characteristic shifts, the changes of threshold voltage and underlying
changes of gate oxide and interface trap densities during the stress
(recovery, annealing) of investigated devices, it is shown that these two
types of stress influence differently on the gate oxide and the SiO2-Si
interface.
The annealing of radiation-induced defects in burn-in stressed n-channel
power VDMOSFETs with thick gate oxides (100 and 120 nm) is analysed. In
comparison with the previous spontaneous recovery, the ...changes of device
electrical parameters observed during annealing are highlighted by the
elevated temperature and voltage applied to the gate, and are more pronounced
in devices with a 120 nm thick gate oxide. The threshold voltage of VDMOSFETs
with a 100 nm thick gate oxide during annealing has an initially slow growth,
but then increases rapidly and reaches the value higher than the
pre-irradiation one (rebound effect). In the case of devices with a 120 nm
thick gate oxide, the threshold voltage behaviour also consists of a slight
initial increase followed by a rapid, but dilatory increase, with an obvious
tendency to achieve the rebound. The changes of channel carrier mobility
during annealing are similar in all samples: at first, it slowly and then
rapidly declines, and after reaching the minimum it begins to increase. In
the case of VDMOSFETs with a thicker gate oxide, these changes are much
slower. The underlying changes in the densities of gate oxide-trapped charge
and interface traps are also delayed in devices with a thicker gate oxide.
All these phenomena occur with certain delay in burn-in stressed devices
compared to unstressed ones. The leading role in the mechanisms responsible
for the observed phenomena is attributed to hydrogen related species.
U ovom radu analizirano je odzarivanje radijacionih defekata kod VDMOS
tranzistora snage sa ultradebelim oksidom gejta (100 nm i 120 nm), koji su
bili podvrgnuti temperaturno-naponskim testovima zarenja. U poredjenju sa
fazom spontanog oporavka prethodno ozracenih tranzistora, pokazano je da su
promene njihovih elektricnih parametara (napon praga i pokretljivosti
nosilaca) tokom odzarivanja prouzrokovane dejstvom povisene temperature i
napona na gejtu. Tokom odzarivanja VDMOS tranzistora snage sa oksidom gejta
debljine 100 nm, posle pocetnog laganog porasta, napon praga naglo pocinje da
raste dostizuci vrednost vecu od one pre ozracivanja. Kod tranzistora sa
oksidom gejta debljine 120 nm, napon praga takodje najpre lagano, a zatim
naglo (ali sa kasnjenjem) raste, sa ociglednom tendencijom da se ispolji
pomenuti skok napona praga. Promene pokretljivosti nosilaca tokom odzarivanja
su slicne kod obe grupe tranzistora: pokretljivost najpre lagano, a zatim
ostro opada, dostize minimum, a zatim pocinje da raste. U slucaju tranzistora
sa debljim oksidom gejta ove promene su znatno sporije. Odgovarajuce promene
gustina naelektrisanja u oksidu i povrsinskih stanja analizirane su sa
aspekta odgovornih mehanizama. Pokazano je da, kod tranzistora sa debljim
oksidom gejta, i promene gustina naelektrisanja u oksidu i povrsinskih stanja
takodje kasne. Svi pomenuti fenomeni tokom odzarivanja najpre su zapazeni kod
kontrolnih uzoraka, a zatim kod uzoraka koji su pre ozracivanja izlozeni
temperaturno-naponskim testovima zarenja. Kljucna uloga u pomenutim
mehanizmima pripisana je vodonikovim cesticama.
PR Projekat Ministarstva nauke Republike Srbije
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