TY - JOUR TI - Influence of Oxygen Content on the Structure and Reliability of Ferroelectric HfxZr1-xO2 Layers AU - Materano, Monica AU - Mittmann, Terence AU - Lomenzo, Patrick D. AU - Zhou, Chuanzhen AU - Jones, Jacob L. AU - Falkowski, Max AU - Kersch, Alfred AU - Mikolajick, Thomas AU - Schroeder, Uwe T2 - ACS APPLIED ELECTRONIC MATERIALS AB - Although some years have passed since the discovery of the ferroelectric phase in HfO2 and ZrO2 and their solid solution system HfxZr1–xO2, the details of the emergence of this phase are still under investigation. Surface energy contribution, dopant inclusion, residual stress, electric field, and oxygen vacancies have been proposed and studied as potential factors that can influence the phase stabilization. In this work, HfxZr1–xO2 layers with different Hf/Zr ratios are deposited via atomic layer deposition (ALD) and physical vapor deposition (PVD) and the amount of oxygen that is supplied during deposition is varied. Results are compared for the two deposition techniques for undoped HfO2 layers. Electrical and structural analysis for the atomic layer-deposited films with different Zr contents and O2 contents is then performed and the reliability of the films when integrated into capacitors is addressed. The results are correlated to the composition of the layers and a model for layer crystallization is suggested. DA - 2020/11/24/ PY - 2020/11/24/ DO - 10.1021/acsaelm.0c00680 VL - 2 IS - 11 SP - 3618-3626 SN - 2637-6113 KW - hafnia KW - ferroelectricity KW - phase analysis KW - orthorhombic phase KW - phase transition KW - oxygen defects KW - atomic layer deposition KW - ferroelectric memory ER - TY - JOUR TI - Hybrid GaAsSb/GaAs Heterostructure Core-Shell Nanowire/Graphene and Photodetector Applications AU - Nalamati, Surya AU - Devkota, Shisir AU - Li, Jia AU - Lavelle, Robert AU - Huet, Benjamin AU - Snyder, David AU - Penn, Aubrey AU - Garcia, Roberto AU - Reynolds, Lewis, Jr. AU - Iyer, Shanthi T2 - ACS APPLIED ELECTRONIC MATERIALS AB - We report the growth of vertical, high-quality GaAs0.9Sb0.1 nanowires (NWs) with improved density on oxygen (O2) plasma-treated monolayer graphene/SiO2/p-Si(111) by self-catalyzed molecular beam epitaxy. An O2 plasma treatment of the graphene under mild conditions enabled modification of the surface functionalization and improved reactivity of the graphene surface to semiconductor adatoms. The rise in the disorder peak of the Raman mode, decreased surface conductivity, and creation of additional O2 groups of plasma-treated graphene compared to that of pristine graphene confirmed functionalization of the graphene. To enhance the nucleation centers further for the vertical yield of NWs on the graphene surface, NWs were grown on a higher Sb composition GaAs0.6Sb0.4 stem for surface engineering the graphene surface via the surfactant effect of Sb and for better lattice matching. The NWs grown under optimal conditions exhibited a zinc blende crystal structure with no discernible structural defects. The NWs with a GaAs-passivated shell exhibited photoluminescence emission at 1.35 eV at 4 K and 1.28 eV at room temperature. The ensemble device fabricated with a top segment of GaAsSb NW-doped n-type using a GaTe captive source exhibited an optical responsivity of 110 A/W with a detectivity of 1.1 × 1014 Jones. These results of hybrid GaAsSb NW heterostructure/graphene devices show significant potential toward the fabrication of flexible near-infrared photodetector device applications. Further, the simple and efficient O2 plasma treatment approach for surface engineering of graphene in conjunction with a high Sb compositional stem has shown to be a promising route that can be broadly applicable for the growth of other III–V ternary material systems for improving the vertical yield of NWs. DA - 2020/// PY - 2020/// DO - 10.1021/acsaelm.0c00433 VL - 2 IS - 10 SP - 3109-3120 ER - TY - JOUR TI - Introduction to x-ray photoelectron spectroscopy AU - Stevie, Fred A. AU - Donley, Carrie L. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - X-ray photoelectron spectroscopy (XPS) has become one of the most widely used surface analysis techniques, and XPS instrumentation has become more user friendly, making the technique available to a large number of researchers. The number of experts in the field, however, has not increased, and XPS data are often misinterpreted in the literature. This paper is intended to provide an introduction to XPS for prospective or novice users. We present the basic principles of the technique including (1) the photoelectric effect, (2) how electrons interact with matter and escape from a surface and how this determines the surface sensitivity of the technique, and (3) how the chemical environment around an element affects the binding energy of its electrons. A description of the instrumentation helps a novice user understand how data are acquired, and information is included on sample preparation and mounting. The important parameters for data acquisition are noted to help guide users starting to acquire data. Interpretation of data on both a qualitative and quantitative level is discussed, and additional sections provide information on more advanced techniques such as angle resolved XPS, small area analysis, near ambient pressure XPS, valence XPS, and ultraviolet photoelectron spectroscopy. DA - 2020/12// PY - 2020/12// DO - 10.1116/6.0000412 VL - 38 IS - 6 SP - SN - 1520-8559 ER - TY - JOUR TI - Sample handling, preparation and mounting for XPS and other surface analytical techniques AU - Stevie, Fred A. AU - Garcia, Roberto AU - Shallenberger, Jeffrey AU - Newman, John G. AU - Donley, Carrie L. T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Sample preparation and mounting are important aspects of x-ray photoelectron spectroscopy (XPS) analysis. New users do not know many techniques that are familiar to analysts with years of experience, and these observations and “tricks of the trade” are typically not published. This article is intended to convey the experience of the authors in this field who have creatively analyzed a wide range of samples. Samples can include solids, powders, fibers, porous solids, and even liquids. This information is also important to anyone submitting samples for analysis, since the preparation of the sample may influence the usefulness of the data collected. These techniques are also applicable to other surface analysis methods. DA - 2020/12// PY - 2020/12// DO - 10.1116/6.0000421 VL - 38 IS - 6 SP - SN - 1520-8559 ER - TY - JOUR TI - Analysis of permethrin treated fabric using ToF-SIMS AU - Zhou, Chuanzhen AU - Stevie, Fred AU - Garcia, Roberto T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Recent studies have shown that it is possible to use ToF-SIMS to identify and quantify mosquito insecticides, such as permethrin and deltamethrin, on mosquito netting. The insecticide in those studies was incorporated in the netting fiber. Permethrin treated fabric is in common usage to provide mosquito repellent clothing and is the only approved insecticide for apparel. The insecticide is applied to the fabric and will no longer be effective after a certain number of washing cycles. ToF-SIMS analyses have now been conducted on fabric composed of nylon and cotton before washing and after 10 and 30 washes to measure the reduction in insecticides. The results show a significant decrease in the insecticide between 10 and 30 washes. The 30 washes sample was known to be no longer effective against mosquitoes. ToF-SIMS was also able to differentiate cotton and nylon fibers. A cross-sectional analysis of cryomicrotomed samples showed the distribution of the insecticide in the individual fibers. The insecticide was found to penetrate completely through the fibers during its application. After ten washes, the insecticide was depleted more rapidly in the cotton than the nylon fibers. The results have implications for the number of acceptable washes for mosquito repellent fabric. DA - 2020/5// PY - 2020/5// DO - 10.1116/1.5141467 VL - 38 IS - 3 SP - SN - 2166-2746 ER - TY - JOUR TI - Effect of Forming Gas Furnace Annealing on the Ferroelectricity and Wake-Up Effect of Hf0.5Zr0.5O2 Thin Films AU - Shekhawat, Aniruddh AU - Walters, Glen AU - Chung, Ching-Chang AU - Garcia, Roberto AU - Liu, Yang AU - Jones, Jacob AU - Nishida, Toshikazu AU - Moghaddam, Saeed T2 - ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY AB - The effect of furnace annealing on the ferroelectricity, leakage current, and wake-up effect in Hf0.5Zr0.5O2 (HZO) ultrathin film is studied as a function of furnace annealing temperature and gas environment after crystallizing the films with rapid thermal annealing in the presence of a TiN capping electrode. HZO films are deposited using atomic layer deposition in a Ge-HZO-TiN stack with Pt as the top contact electrode. The increment in the remanent polarization (Pr) is higher when the films are furnace annealed in the forming gas ambient. Forming gas furnace annealed films show an order of magnitude less leakage current as compared to the nitrogen annealed films. Dynamic hysteresis current measurements of the HZO ultrathin films show a faster merging of the four switching peaks after cycling the virgin forming gas furnace annealed films. H-incorporation during forming gas furnace annealing does not degrade the ferroelectric properties of HZO ultrathin films unlike conventional ferroelectrics, such as PZT or SBT. Higher Pr, lower leakage current, and an improved wake-up effect of the HZO ultrathin films show its resistance to degradation by forming gas furnace annealing, which makes ferroelectric HfO2 an ideal material for next-generation ferroelectric memory devices. DA - 2020/1/24/ PY - 2020/1/24/ DO - 10.1149/2162-8777/ab6b13 VL - 9 IS - 2 SP - SN - 2162-8777 ER - TY - JOUR TI - A multi-proxy study of changing environmental conditions in a Younger Dryas sequence in southwestern Manitoba, Canada, and evidence for an extraterrestrial event AU - Teller, James AU - Boyd, Matthew AU - LeCompte, Malcolm AU - Kennett, James AU - West, Allen AU - Telka, Alice AU - Diaz, Aura AU - Adedeji, Victor AU - Batchelor, Dale AU - Mooney, Charles AU - Garcia, Roberto T2 - QUATERNARY RESEARCH AB - Abstract Multi-proxy analyses of a sequence spanning the Younger Dryas (YD) in the Glacial Lake Hind basin of Manitoba provides insight into regional paleohydrology and paleovegetation of meltwater rivers and lakes spanning >4000 yr; the sequence is controlled by 25 new accelerator mass spectrometry ages. This lake, dammed by the Laurentide Ice Sheet, overflowed into Lake Agassiz. The pre-YD interval records rapid sedimentation from meltwaters that headed in proglacial lakes in the Canadian Prairies that are known to have been catastrophically released when ice or sediment barriers were breached. Pollen in this phase is dominated by pre-Quaternary forms eroded from Paleocene bedrock. At the onset of the YD at ~12.8 cal ka, the sudden appearance of concentrations of nanodiamonds, high-temperature magnetic spherules, platinum, and iridium provide evidence of an extraterrestrial (ET) event that others have identified at more than 40 sites in North America. Major changes in oceans and climate, and the catastrophic outflow of nearby Lake Agassiz at the onset of the YD, may be related. Lower water levels and a reduction of Souris River inflow to Lake Hind followed, which are reflected by more clayey and organic-rich sediments and a decrease in pre-Quaternary palynomorphs. This may have resulted from the deepening of river valleys caused by the release of meltwater triggered by the ET event. Wetlands then began to develop, leading to peat deposition from 12.3 to 11 cal ka. This was followed by a fluvial episode depositing sand and then by increased Holocene aridity that resulted in accumulation of a thick sequence of dune sands. A dry woodland environment with a mix of conifers (especially Picea and Larix ) and deciduous trees (especially Populus and Quercus ) covered the uplands from ~13 to 10 cal ka. DA - 2020/1// PY - 2020/1// DO - 10.1017/qua.2019.46 VL - 93 IS - 1 SP - 60-87 SN - 1096-0287 KW - Glacial lake KW - Manitoba KW - Younger Dryas KW - Paleoecology KW - Floods KW - Extraterrestrial event ER -