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Fabrication and Characterization of Ion-Doped p-Type Nanocrystalline Silicon Thin-Film Transistors
Yassine Djeridane,Pere Roca i Cabarrocas,김가현,김세환,배정호,정준영,장진 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
We report on the fabrication of coplanar p-channel nanocrystalline silicon thin-film transistors (nc-Si TFT) by using conventional boron ion doping. p-channel TFTs are necessary to implement complementary metal-oxide-semiconductor (CMOS) circuits with low power consumption, but amorphous silicon and polycrystalline silicon p-channel TFTs both have drawbacks, such as low hole mobility, high cost and poor uniformity. On the other hand, nanocrystalline silicon shows many merits, encouraging its use in CMOS circuits such as reasonable carrier mobility, high uniformity and ease of processing, despite these advantages, very few studies of p-type nanocrystalline silicon TFTs have been performed and there have been no documented efforts to adopt an ion-doped coplanar structure or to optimize its fabrication process. The TFTs presented herein have been fabricated using a conventional ion-doping process and show reasonably optimized characteristics, so the result demonstrated in this paper can be immediately adopted in a large-area, industrial system with little adjustment. Moreover, it is quite a new concept to use nanocrystalline silicon thin films for coplanar p-channel TFTs. The nanocrystalline silicon thin-films used in this work were grown on glass substrates at a low substrate temperature of 200 ℃ by using a SiF<SUB>4</SUB>/H<SUB>2</SUB>/Ar mixture. The TFTs that resulted from these films exhibited a field-effect mobility of 1.52 cm<SUP>2</SUP>/Vs, a gate voltage swing of 1.1 V/dec, an on/off ratio in excess of 10<SUP>6</SUP> and a threshold voltage of −6.28 V.
Studies of the Stability of Microcrystaline Silicon Bottom-Gate TFTs under Electrical Stress
Oumkelthoum Moustapha,Alexey Abramov,Y. Bonnassieux,P. Roca i Cabarroca,H. Y. Choe 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
We present, in this paper, the stability results under bias stres of n-type microcrystaline silicon (μc-Si:H) botom- gate thin-film transistors (TFTs) with various intrinsic layer compositions (a single μc-Si layer or a dual intrinsic layer made of a-Si:H and μc-Si). TFTs were fabricated using the conventional amorphous silicon (a-Si:H) TFT proces(low temperature Plasma Enhanced Chemical Vapor Deposition). Our results suggest that the dual layer structure is advantageous in terms of procesing while keping good mobility and stability. After 24 hr of electrical stres the threshold voltage drift (ΔV<SUB>T</SUB>) was les than 0.2 V and mobility drift (Δμ) was about 8 %. In order to understand the causes of the instability, experimental analyses were performed; they showed that charge trapping at the interface was responsible for the degradation in the TFTs. Simulation of the impact of threshold voltage (V<SUB>T</SUB>) and the mobility drifts showed that a 1-V variation in V<SUB>T</SUB> induced a variation of 36 % in OLED curent and that a variation of 20 % in the mobility leads to a 23 % variation in the OLED curent.
Kim, Ka-Hyun,Johnson, Erik V.,Roca i Cabarrocas, Pere Institute of Pure and Applied Physics 2016 Japanese Journal of Applied Physics Vol.55 No.7
<P>Hydrogenated polymorphous silicon (pm-Si:H) is a material consisting of a small volume fraction of nanocrystals embedded in an amorphous matrix. pm-Si:H solar cells demonstrate interesting initial degradation behaviors such as rapid initial change in photovoltaic parameters and self-healing after degradation during light-soaking. The precise dynamics of the light-induced degradation was studied in a series of light-soaking experiments under various illumination conditions such as AM1.5G and filtered 570 nm yellow light. Hydrogen effusion experiment before and after light-soaking further revealed that the initial degradation of pm-Si:H solar cells originate from the modification of silicon-hydrogen bonding on the surface of silicon nanocrystals in pm-Si:H. (C) 2016 The Japan Society of Applied Physics.</P>
Kim, Ka-Hyun,Johnson, Erik V.,Cabarrocas, Pere Roca i American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.7
<P>Hydrogenated polymorphous silicon (pm-Si:H) is a material consisting of a small volume fraction of nanocrystals embedded in an amorphous matrix, and which can be grown at high deposition rates by increasing the radio-frequency power. When grown at high deposition rates, pm-Si: H films show a shift of their infrared (IR) absorption stretching band peak to higher wavenumbers and a sudden increase in their optical bandgap. The IR absorption spectrum was analyzed by deconvolution into three bands, including a medium stretching mode positioned at 2030 cm(-1), which has been attributed to Si-H bonds at silicon nanocrystal surfaces. Secondary ion mass spectrometry measurements confirmed that an excess of hydrogen is incorporated in pm-Si: H grown at high deposition rate, leading to a sharp increase in the optical bandgap. We suggest that this sharp increase can be used as a simple tool to detect the deterioration of material quality when using high deposition rate processes.</P>
Electronic properties of embedded graphene: doped amorphous silicon/CVD graphene heterostructures
Arezki, Hakim,Boutchich, Mohamed,Alamarguy, David,Madouri, Ali,Alvarez, José,Cabarrocas, Pere Roca i,Kleider, Jean-Paul,Yao, Fei,Hee Lee, Young IOP 2016 Journal of Physics, Condensed Matter Vol.28 No.40
<P>Large-area graphene film is of great interest for a wide spectrum of electronic applications, such as field effect devices, displays, and solar cells, among many others. Here, we fabricated heterostructures composed of graphene (Gr) grown by chemical vapor deposition (CVD) on copper substrate and transferred to SiO<SUB>2</SUB>/Si substrates, capped by n‑ or p-type doped amorphous silicon (a-Si:H) deposited by plasma-enhanced chemical vapor deposition. Using Raman scattering we show that despite the mechanical strain induced by the a-Si:H deposition, the structural integrity of the graphene is preserved. Moreover, Hall effect measurements directly on the embedded graphene show that the electronic properties of CVD graphene can be modulated according to the doping type of the a-Si:H as well as its phase i.e. amorphous or nanocrystalline. The sheet resistance varies from 360 Ω sq<SUP>−1</SUP> to 1260 Ω sq<SUP>−1</SUP> for the (p)-a-Si:H/Gr (n)-a-Si:H/Gr, respectively. We observed a temperature independent hole mobility of up to 1400 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> indicating that charge impurity is the principal mechanism limiting the transport in this heterostructure. We have demonstrated that embedding CVD graphene under a-Si:H is a viable route for large scale graphene based solar cells or display applications.</P>
Absorbing one-dimensional planar photonic crystal for amorphous silicon solar cell
El Daif, Ounsi,Drouard, Emmanuel,Gomard, Guillaume,Kaminski, Anne,Fave, Alain,Lemiti, Mustapha,Ahn, Sungmo,Kim, Sihan,Roca i Cabarrocas, Pere,Jeon, Heonsu,Seassal, Christian The Optical Society 2010 Optics express Vol.18 No.suppl3
<P>We report on the absorption of a 100nm thick hydrogenated amorphous silicon layer patterned as a planar photonic crystal (PPC), using laser holography and reactive ion etching. Compared to an unpatterned layer, electromagnetic simulation and optical measurements both show a 50% increase of the absorption over the 0.38-0.75micron spectral range, in the case of a one-dimensional PPC. Such absorbing photonic crystals, combined with transparent and conductive layers, may be at the basis of new photovoltaic solar cells.</P>