Integration of epitaxial LiNbO3thin films with silicon technology.

Development of bulk acoustic wave filters with ultra-wide pass bands and operating at high frequencies for 5thand 6thgeneration telecommunication applications and micro-scale actuators, energy harvesters and sensors requires lead-free piezoelectric thin films with high electromechanical coupling and compatible with Si technology. In this paper, the epitaxial growth of 36°Y-X and 30°X-Y LiNbO3films by direct liquid injection chemical vapour deposition on Si substrates by using epitaxial SrTiO3layers, grown by molecular beam epitaxy, has been demonstrated. The stability of the interfaces and chemical interactions between SrTiO3, LiNbO3and Si were studied experimentally and by thermodynamical calculations. The experimental conditions for pure 36°Y-X orientation growth have been optimized. The piezoelectricity of epitaxial 36°Y-X LiNbO3/SrTiO3/Si films was confirmed by means of piezoelectric force microscopy measurements and the ferroelectric domain inversion was attained at 85 kV.cm-1as expected for the nearly stoichiometric LiNbO3. According to the theoretical calculations, 36°Y-X LiNbO3films on Si could offer an electromechanical coupling of 24.4% for thickness extension excitation of bulk acoustic waves and a comparable figure of merit of actuators and vibrational energy harvesters to that of standard PbZr1-xTixO3films.

Ferroelectric Hf0.5Zr0.5O2 films with improved endurance obtained through low temperature epitaxial growth on seed layers.

Crystallization temperature is a critical parameter in the stabilization of the metastable ferroelectric phase of HfO2. The optimal crystallization temperature used for polycrystalline films is too low to grow epitaxial films. We have developed a new growth strategy, based on the use of an ultrathin seed layer, to obtain high-quality epitaxial films of orthorhombic Hf0.5Zr0.5O2 at a lower temperature. The threshold temperature for epitaxy is reduced from about 750 °C to about 550 °C using a seed layer. Epitaxial films deposited at low temperatures exhibit highly enhanced endurance, and films grown at 550-600 °C show high polarization, no wake-up effect, and greatly reduced fatigue and improved endurance in comparison with the films deposited at high temperatures without a seed layer. We propose that the endurance enhancement is due to a positive effect of the defects, which limits the propagation of pinned ferroelectric domains.

Integration of Li4Ti5O12 Crystalline Films on Silicon Toward High-Rate Performance Lithionic Devices.

The growth of crystalline Li-based oxide thin films on silicon substrates is essential for the integration of next-generation solid-state lithionic and electronic devices including on-chip microbatteries, memristors, and sensors. However, growing crystalline oxides directly on silicon typically requires high temperatures and oxygen partial pressures, which leads to the formation of undesired chemical species at the interface compromising the crystal quality of the films. In this work, we employ a 2 nm gamma-alumina (γ-Al2O3) buffer layer on Si substrates in order to grow crystalline thin films of Li4Ti5O12 (LTO), a well-known active material for lithium-ion batteries. The ultrathin γ-Al2O3 layer enables the formation of a stable heterostructure with sharp interfaces and drastically improves the LTO crystallographic and electrochemical properties. Long-term galvanostatic cycling of 50 nm LTO films in liquid-based half-cells demonstrates a high capacity retention of 91% after 5000 cycles at 100 C. Rate capability tests showcase a specific charge of 56 mA h g-1 at an exceptional C-rate of 5000 C (15 mA cm-2). Moreover, with sub-millisecond current pulse tests, the reported thin-film heterostructure exhibits rapid Li-ion (de)intercalation, which could lead to fast switching timescales in resistive memory devices and electrochemical transistors.

An innovative therapeutic educational program to support older drivers with cognitive disorders: Description of a randomized controlled trial study protocol.

Older drivers face the prospect of having to adjust their driving habits because of health problems, which can include neurocognitive disorders. Self-awareness of driving difficulties and the interaction between individual with neurocognitive disorders and natural caregiver seem to be important levers for the implementation of adaptation strategies and for the subsequent voluntary cessation of driving when the cognitive disorders become too severe. This study aims to evaluate an educational program for patient/natural caregiver dyads who wish to implement self-regulation strategies in driving activity, and to improve self-awareness of driving ability. The ACCOMPAGNE program is based on seven group workshops, which target the dyad. The workshops deal with the impact of cognitive, sensory and iatrogenic disorders on driving. They tackle questions about responsibility, and about autonomy and social life. They also provide alternative solutions aimed at maintaining outward-looking activities even if driving is reduced or stopped. A randomized controlled trial is planned to evaluate the effectiveness of the program 2 months and 6 months after inclusion, and to compare this to the effectiveness of conventional approaches. The main outcome of this trial (i.e., the implementation of self-regulated driving strategies), will be measured based on scores on the "Current Self-Regulatory Practices" subscale of the Driver Perception and Practices Questionnaire. The Driving Habits Questionnaire will be used to measure secondary outcomes (indicators of driving changes; indicators of changes in mood, quality of life and caregiver burden; and self-awareness of driving abilities). Indicators will be collected for both patients and natural caregivers. This cognitive, social and psychological program should allow older individuals with cognitive disorders to drive more safely, and help to maintain the quality of life and mood of both patient and natural caregiver despite driving limitations. The patient's care path would be optimized, as he/she would become an actor in the process of giving up driving, which will, most certainly, be needed at some point in the progress of neurocognitive disorders. This process ranges from becoming aware of driving difficulties, to implementing self-regulation strategies, through to complete cessation of driving when necessary. Clinical trial registration number: NCT04493957.

Anxiety symptoms during COVID-19 in older adults with psychiatric disorders.

Objective: During the COVID-19 pandemic, older people and patients with psychiatric disorders had an increased risk of being isolated. The French National Authority for Health has recommended a reinforced follow-up of these patients. Cross-sectional studies reported an increased risk of developing anxiety and depression during pandemic. The aim of our study was to identify factors associated with higher anxiety during the pandemic in older patients with psychiatric disorders. Methods: STERACOVID is a multicenter cohort study with 117 patients followed-up by phone in two French geriatric psychiatry units. In this work, we used cross-sectional data from a prospective follow-up conducted between January and May 2021. Results: We found that coping strategies, personality, and living conditions were associated with general anxiety (GA) level during the pandemic period. Higher GA was associated with less positive thinking coping strategy, more avoidance strategies, a lower level of extraversion, a higher level of neuroticism, more time spent watching the news, a higher feeling of loneliness, and a lack of physical contact. Findings: Our study identified factors associated with a poorer experience of pandemic crisis. Special attention should be paid to patients with a high level of neuroticism and a high feeling of loneliness. Support could aim to help patients use more functional strategies: reducing avoidance strategies and increasing positive thinking. Finally, reducing time watching news could also be an interesting prevention perspective. Clinical trial registration: clinicaltrials.gov, identifier NCT04760795.

Harmonisation and Between-Country Differences of the Lifetime of Experiences Questionnaire in Older Adults.

Background: The Lifetime of Experiences Questionnaire (LEQ) assesses complex mental activity across the life-course and has been associated with brain and cognitive health. The different education systems and occupation classifications across countries represent a challenge for international comparisons. The objectives of this study were four-fold: to adapt and harmonise the LEQ across four European countries, assess its validity across countries, explore its association with brain and cognition and begin to investigate between-country differences in life-course mental activities. Method: The LEQ was administered to 359 cognitively unimpaired older adults (mean age and education: 71.2, 13.2 years) from IMAP and EU-funded Medit-Ageing projects. Education systems, classification of occupations and scoring guidelines were adapted to allow comparisons between France, Germany, Spain and United Kingdom. We assessed the LEQ's (i) concurrent validity with a similar instrument (cognitive activities questionnaire - CAQ) and its structural validity by testing the factors' structure across countries, (ii) we investigated its association with cognition and neuroimaging, and (iii) compared its scores between countries. Results: The LEQ showed moderate to strong positive associations with the CAQ and revealed a stable multidimensional structure across countries that was similar to the original LEQ. The LEQ was positively associated with global cognition. Between-country differences were observed in leisure activities across the life-course. Conclusions: The LEQ is a promising tool for assessing the multidimensional construct of cognitive reserve and can be used to measure socio-behavioural determinants of cognitive reserve in older adults across countries. Longitudinal studies are warranted to test further its clinical utility.

Impact of La Concentration on Ferroelectricity of La-Doped HfO2 Epitaxial Thin Films.

Epitaxial thin films of HfO2 doped with La have been grown on SrTiO3(001) and Si(001), and the impact of the La concentration on the stabilization of the ferroelectric phase has been determined. Films with 2-5 at. % La doping present the least amount of paraelectric monoclinic and cubic phases and exhibit the highest polarization, having a remanent polarization above 20 µC/cm2. The dopant concentration results in an important effect on the coercive field, which is reduced with increasing La content. Combined high polarization, high retention, and high endurance of at least 1010 cycles is obtained in 5 at. % La-doped films.

Mental Health of People with Dementia During COVID-19 Pandemic: What Have We Learned from the First Wave?

BACKGROUND: People with dementia (PWD) and their caregivers are populations highly vulnerable to COVID-19 pandemic and its consequences. A better knowledge of the living conditions during the first lockdown is necessary to prevent the risk of poor mental health (PMH) in this population. OBJECTIVE: The present study aimed to compare the mental health of caregivers of PWD living at home or in nursing-homes and to identify specific factors influencing their mental health. METHODS: We conducted an anonymous cross-sectional online survey in France from March 17 to May 11, 2020. Three hundred and eighty-nine caregivers accompanying a PWD living at home (HC) and 159 accompanying a PWD living in a nursing home (NHC) participated in the study. Caregivers' mental health including anxiety, depression, stress, and burden was assessed with self-reported standardized scales. RESULTS: Half of the caregivers exhibited PMH, including depression, anxiety, or self-reported stress. Similar PMH rates were provided whatever the PWD place of residence. Regarding HC, our results also highlighted a number of risk factors for PMH, including the fact that caregiver live with PWD, to give increased support to PWD, and to feel more isolated for managing PWD since lockdown. CONCLUSION: PMH was observed for caregivers of PWD during lockdown, whatever PWD living place, suggesting that concern for PWD may explain more of caregiver distress than increased material tasks. In the future, it will be necessary to pay attention to caregivers after the crisis by estimating the longer-term impact on their mental health.

COVID-19: Association Between Increase of Behavioral and Psychological Symptoms of Dementia During Lockdown and Caregivers' Poor Mental Health.

BACKGROUND: From March 2020, the support and care systems for caregivers and people with dementia (PWD) were suspended or dramatically changed due to the lockdown during the world pandemic of COVID-19. Thus, these changes in living conditions have had deleterious consequences on the behavior of PWD and subsequently on their caregivers' mental health, the two being linked. OBJECTIVE: Our study aimed to examine changes in behavior among PWD and to look for associations between the evolution of behavioral and psychological symptoms of dementia (BPSD) and caregivers' mental health in the context of COVID-19. METHODS: The study was conducted among caregivers of PWD living at home in France. Caregivers were interviewed via an anonymous cross-sectional online survey during the first lockdown between April 15 and June 15, 2020. RESULTS: Three hundred and eighty-nine caregivers accompanying a relative living at home participated in the study; 43.3%of the PWD presented a worsening of BPSD during the lockdown. With multivariate logistic regressions, a significant association was observed between "more BPSD" and burden, anxiety and depression, between "BPSD equivalent" and anxiety and depression, and between "emerging BPSD" and only depression. CONCLUSION: The lockdown seems to have an impact on behavioral disorders in PWD and these disorders are associated with poorer mental health of caregivers. Our findings suggest attention should be given to caregivers of PWD who have BPSD before lockdown and the need for continued consultations and professional help in case of new lockdowns.

Immediate Benefit of Art on Pain and Well-Being in Community-Dwelling Patients with Mild Alzheimer's.

OBJECTIVE: The present report aims to evaluate whether singing intervention can bring an immediate benefit that is greater than the one provided by painting intervention on pain and well-being. METHODS: Fifty-nine mild patients with Alzheimer disease were randomized to a 12-week singing (n = 31) or painting group (n = 28). In the present analysis, the immediate evolution of pain and well-being was compared across sessions between the 2 groups using mixed-effects models. RESULTS: We observed a significant improvement in well-being for both singing and painting groups immediately after sessions, compared to the assessment before the sessions. We did not observe this improvement across the sessions for pain intensity measurement. DISCUSSION: Our results revealed that both painting and singing interventions provide an immediate benefit on the patients' well-being.

Electric and Mechanical Switching of Ferroelectric and Resistive States in Semiconducting BaTiO3-δ Films on Silicon.

Materials that can couple electrical and mechanical properties constitute a key element of smart actuators, energy harvesters, or many sensing devices. Within this class, functional oxides display specific mesoscale responses which often result in great sensitivity to small external stimuli. Here, a novel combination of molecular beam epitaxy and a water-based chemical-solution method is used for the design of mechanically controlled multilevel device integrated on silicon. In particular, the possibility of adding extra functionalities to a ferroelectric oxide heterostructure by n-doping and nanostructuring a BaTiO3 thin film on Si(001) is explored. It is found that the ferroelectric polarization can be reversed, and resistive switching can be measured, upon a mechanical load in epitaxial BaTiO3-δ /La0.7 Sr0.3 MnO3 /SrTiO3 /Si columnar nanostructures. A flexoelectric effect is found, stemming from substantial strain gradients that can be created with moderate loads. Simultaneously, mechanical effects on the local conductivity can be used to modulate a nonvolatile resistive state of the BaTiO3-δ heterostructure. As a result, three different configurations of the system become accessible on top of the usual voltage reversal of polarization and resistive states.

Thermoelectric La-doped SrTiO3 epitaxial layers with single-crystal quality: from nano to micrometers.

High-quality thermoelectric La0.2Sr0.8TiO3 (LSTO) films, with thicknesses ranging from 20 nm to 0.7 µm, have been epitaxially grown on SrTiO3(001) substrates by enhanced solid-source oxide molecular-beam epitaxy. All films are atomically flat (with rms roughness < 0.2 nm), with low mosaicity (<0.1°), and present very low electrical resistivity (<5 × 10-4 Ω cm at room temperature), one order of magnitude lower than standard commercial Nb-doped SrTiO3 single-crystalline substrate. The conservation of transport properties within this thickness range has been confirmed by thermoelectric measurements where Seebeck coefficients of approximately -60 µV/K have been recorded for all films. These LSTO films can be integrated on Si for non-volatile memory structures or opto-microelectronic devices, functioning as transparent conductors or thermoelectric elements.

Tuning the local frictional and electrostatic responses of nanostructured SrTiO(3)-surfaces by self-assembled molecular monolayers.

Exploiting the capability of preparing nanostructured bifunctional terminated SrTiO(3) substrates (SrO and TiO(2)), the surface properties have been locally tuned by employing a double bottom-up strategy which combines the use of chemically nanopatterned substrates with molecular self-assembly. The dynamics of surface diffusion that allows SrO and TiO(2) chemical-termination nano-patterning of the SrTiO(3) is first addressed. Second, termination-dependent heterogeneous nucleation is used to demonstrate that stearic acid selectively grows on the TiO(2) terminated terraces. This adsorption improves the frictional properties and modifies the surface contact potential. The possibility of simultaneously tailoring at the nanoscale different surface properties of widely employed oxide substrates is promising for building up new devices useful for emerging applications.