All-Inorganic Bismuth Halide Perovskite-Like Materials A₃Bi₂I₉ and A₃Bi_1.8Na_0.2I_8.6 (A = Rb and Cs) for Low-Voltage Switching Resistive Memory

Cuhadar, Can,Kim, Seul-Gi,Yang, June-Mo,Seo, Ja-Young,Lee, Donghwa,Park, Nam-Gyu American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.35

<P>As silicon-based metal oxide semiconductor field effect transistors get closer to their scaling limit, the importance of resistive random-access memory devices increases due to their low power consumption, high endurance and retention performance, scalability, and fast switching speed. In the last couple of years, organic-inorganic lead halide perovskites have been used for resistive switching applications, where they outperformed conventional metal oxides in terms of large on/off ratio and low power consumption. However, there were scarce reports on lead-free perovskites for such applications. In this report, we prepared lead-free Au/A<SUB>3</SUB>Bi<SUB>2</SUB>I<SUB>9</SUB>/Pt/Ti/SiO<SUB>2</SUB>/Si (A is either Cs<SUP>+</SUP> or Rb<SUP>+</SUP>) devices and tested their resistive switching characteristics. They showed a forming step prior to repeating switching, low operating voltage (0.09 V for Rb<SUB>3</SUB>Bi<SUB>2</SUB>I<SUB>9</SUB> and 0.1 V for Cs<SUB>3</SUB>Bi<SUB>2</SUB>I<SUB>9</SUB>), large on/off ratio (>10<SUP>7</SUP>), relatively high endurance (200 cycles for Rb<SUB>3</SUB>Bi<SUB>2</SUB>I<SUB>9</SUB> and 400 cycles for Cs<SUB>3</SUB>Bi<SUB>2</SUB>I<SUB>9</SUB> cycles), and high retention (1000 s). Such low voltage could be explained by grain boundary-modulated ion drift. Difference in endurance was speculated to be due to the difference in the surface roughness of films because Cs<SUB>3</SUB>Bi<SUB>2</SUB>I<SUB>9</SUB> films are smoother. To get rid of the forming step, 10% of the Bi<SUP>3+</SUP> cations were substituted with Na<SUP>+</SUP> cations. However, this method only worked on Rb-based structures. This phenomenon was explained by the defect formation energy, which can only be negative in a corner-sharing Rb<SUB>3</SUB>Bi<SUB>2</SUB>I<SUB>9</SUB> structure compared to a face-sharing octahedral Cs<SUB>3</SUB>Bi<SUB>2</SUB>I<SUB>9</SUB> structure. As a result, the forming step was removed, and 100 cycles endurance and 1000 s retention performance were obtained. Similarly, the lower endurance is suspected to be due to the poor surface quality of the film.</P> [FIG OMISSION]</BR>

The Aspects, Reasons and Outcomes of an Unmanned Air Vehicle Crash Caused By Engine Failure

Cuhadar, Ismet,Dursun, Mahir The Society for Aerospace System Engineering 2015 International Journal of Aerospace System Engineer Vol.2 No.1

The Unmanned Air Vehicle (UAV) systems are indispensable tools of air surveillance and reconnaissance nowadays. Via this systems, hazardous end risky intelligence gathering activities are handled easily. Although they are named as "Unmanned" the UAV systems are commanded by pilots/operators. So, because of weather conditions, enemy attacks etc. as well as pilot error it is possible to face with sudden Round per Minute (RPM) drops and subsequently engine cut/stop during a mission flight at high altitudes. In this case, there are some very urgent decisions to make and rapid "emergency procedure" steps to take in a very short time before Line of Sight (LOS) is lost. The time before crash and the distance to landing air base need to be calculated, the Return Home route need to be checked and the landing/crash side need to be determined. Therefore it is a vital necessity that UAV pilots have some extra qualifications like being determined, well instructed and trained, experienced apart from operating ability. Within this scope, for an education process of a UAV pilot experience sharing and lessons learned are as important as simulators even more. By means of lessons learned it is possible to find out the reasons, mistakes and prevent the likely UAV accidents. In this study it is told about a real UAV crash, experienced of the pilot, the dos and don'ts and the difficulties. Thus it is aimed to help the people who can experience the same or similar situations in future.

Does the Impairment of Functional Life Increase the Probability of Suicide in Cancer Patients?

Tanriverdi, Derya,Cuhadar, Dondu,Ciftci, Serpil Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.21

Background: Cancer affects patients in many ways including physical, social, emotional, psychological and economic and restricts the functional lives. Psychiatric problems seen among cancer patients may increase the suicide probability and patients perceive suicide as a peaceful death type. The aim of this study was to examine the correlation between functional life and suicide probability among cancer patients. Materials and Methods: This study was conducted with 105 cancer patients as descriptive. The Functional Living Index_Cancer (FLIC)," suicide probability scale" (SPS) and personal information form were used as data collecting tools. Data were evaluated by descriptive analysis, and Pearson's correlation. Results: It was determined that 34.3% of patients thought of suicide. Significant negative correlation was found between functional life and suicide probability (r=-.641, p=0.000), increase being evident in those with poor functional life. Conclusions: It is recommended that cancer patients should be supported for improving their functional lives with help in coping processes for illness and treatment symptoms. Evaluation of the patient mental status to prevent the suicide among this group is an important role for nurses.

Prognostic Significance of Circulating Tumor Cells and Serum CA15-3 Levels in Metastatic Breast Cancer, Single Center Experience, Preliminary Results

Tarhan, Mustafa Oktay,Gonel, Ataman,Kucukzeybek, Yuksel,Erten, Cigdem,Cuhadar, Serap,Yigit, Seyran Ceri,Atay, Aysenur,Somali, Isil,Dirican, Ahmet,Demir, Lutfiye,Koseoglu, Mehmet Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.3

Background: Breast cancer is the second leading cancer causing death in women. Circulating tumor cells are among the prognostic factors while tumor markers are of diagnostic value and can be used for follow-up. The aim of this study was to investigate the correlation between the prognostic significance of the serum CA15-3 levels, number of circulating tumor cells and histopathological tumor factors. Materials and Methods: Thirty patients recently diagnosed with breast cancer were included in the study. Number of circulating tumor cells and serum CA15-3 level were assessed when metastasis was detected and diagnostic value was assessed. Presence of associations with estrogen and progesterone receptors, c-erbB2, Ki-67 proliferation index and histological grade were also evaluated. Results: Median overall survival of the patients with serum CA15-3 levels of >108 ng/dl was 19 months whereas for those with a low serum level it was 62 months. Median overall survival for CTC ${\geq}5$ vs CTC<5 patients was 19 months and 40 months respectively. The difference between the two groups was statistically significant. Conclusions: Prognostic significance of the CTC count and CA15-3 levels in metastatic breast cancer patients was demonstrated.

The effect of compositional engineering of imidazolium lead iodide on the resistive switching properties

Choi, Eun-Suk,Yang, June-Mo,Kim, Seul-Gi,Cuhadar, Can,Kim, So-Yeon,Kim, Seong Hun,Lee, Donghwa,Park, Nam-Gyu Royal Society of Chemistry 2019 Nanoscale Vol.11 No.30

<P>We report here resistive switching memory characteristics of imidazolium lead iodide depending on the molar ratio of PbI2 to imidazolium iodide (ImI), that is, PbI2 : ImI = 1 : 0, 1 : 0.5, 1 : 1, 1 : 2, 1 : 3 and 0 : 1. X-ray diffraction confirms that the stoichiometric composition results in a hexagonal structure of (Im)PbI3, showing a one-dimensional face-sharing [PbI3<SUP>−</SUP>] chain. Bipolar resistive switching characteristics are observed regardless of the mixing ratio, where the forming process is required prior to SET and RESET processes at around +0.2 V and −0.2 V, respectively. The ON/OFF ratio is increased from 10<SUP>6</SUP> to 10<SUP>9</SUP> as the ImI content is increased due to the increased HRS associated with the pronounced insulating characteristics by ImI, whereas, the stoichiometric (Im)PbI3 exhibits 5 times longer endurance (10<SUP>3</SUP>) and an order of magnitude longer retention time (10<SUP>4</SUP> s) as compared to other compositions. Multilevel data storage capability is confirmed by changing the compliance current. The low resistance state (LRS) and the high resistance state (HRS) are associated with Ohmic conduction and Schottky conduction, respectively. Density functional theory (DFT) calculation reveals that the defect formation energy of iodine vacancy is estimated to be low indicating that (Im)PbI3 has a sufficient concentration of iodide vacancy for filament formation. Further energy barrier calculations show that iodide migration preferentially occurs along the 1-dimensional [234] crystallographic direction rather than the interlayer [130] direction. A good performance of the (Im)PbI3-based memristor is thus related to the low defect formation energy of iodide vacancy and the preferential growth of the filament along the 1-dimensional chain.</P>

Wafer-scale reliable switching memory based on 2-dimensional layered organic-inorganic halide perovskite

Seo, J. Y.,Choi, J.,Kim, H. S.,Kim, J.,Yang, J. M.,Cuhadar, C.,Han, J.,Kim, S. J.,Lee, D.,Jang, H. Royal Society of Chemistry 2017 Nanoscale Vol.9 No.40