JPS61294454A - Photosensitive body - Google Patents

Abstract

PURPOSE:To obtain a stable picture quality having a less tendency for an image flow by laminating each specific an electric charge blocking layer, an electric charge transfer layer, an electric charge generating layer, an intermediate layer and a surface reforming layer in order on a substrate. CONSTITUTION:The photosensitive body 39 is laminated the N<+> type electric charge blocking layer 44 composed of a-Si:H which is heavily doped with an element belonging to the group Va of the periodic table of the element, and contains one of the atoms of C, N, and O, and the electric charge transfer layer 42 composed of a-Si:H which is made an intrinsic, by lightly doping it with an element belonging to the group IIIa of the periodic table of the element, and contains atoms C and O in order on the drum shaped conductive substrate 41 composed of Al. The titled body is constituted by laminating the electric charge generating layer 43 composed of a-Si:H the intermediate layer 46 composed of a P<+> or N<+> type amorphous hydrogenated silicon which is heavily doped with an element belonging to the group IIIa or Va of the periodic table of the element, and the surface reforming layer 45 composed of an amorphous hydrogenated silicon which is made to a P-type or an N-type or an intrinsic by doping it with an element belonging to the group IIIa or Va of the periodic table of the element, and contains one of atoms of N, C and O atoms.

Description

[Detailed description of the invention]

B. Industrial Application Field The present invention relates to a photoreceptor, for example, an electrophotographic photoreceptor. Conventional technology Conventionally, as an electrophotographic photoreceptor, Se or Se has A S
Photoreceptors doped with % T e SS b and the like, photoreceptors in which ZnO or CdS is dispersed in a resin binder, and the like are known. However, these photoreceptors are environmentally polluting and
There are problems with thermal stability and mechanical strength. On the other hand, electrophotographic photoreceptors using amorphous silicon (a-3i) as a matrix have been proposed in recent years. a-3t has a so-called dangling bond in which the bond of Si-3i is broken, and many localized levels exist within the energy gap due to this defect. For this reason, hopping conduction of thermally excited carriers occurs, resulting in a small dark resistance, and photoexcited carriers are trapped in localized levels, resulting in poor photoconductivity. Therefore, the dangling bonds are filled by compensating the defects with hydrogen atoms (H) and bonding H to Si. Such amorphous hydrogenated silicon (hereinafter referred to as a-3
It is called t:H. ) has a resistivity in the dark of 108 to 10
9Ω - country, about 1 compared to amorphous Se
It's even lower than 1/10,000. Therefore, a photoreceptor made of a single layer of a-3i:H has problems in that the dark decay rate of the surface potential is high and the initial charging potential is low. However, on the other hand, when irradiated with light in the visible and infrared regions, the resistivity increases (decreases), so it has extremely excellent characteristics as a photosensitive layer of a photoreceptor. -3t: a-3i with H as base material
An electrophotographic copying machine incorporating a system photoreceptor 9 is shown. According to this copying machine, a glass document mounting table 3 on which a document 2 is placed and a platen cover 4 that covers the document 2 are disposed in the upper part of a cabinet 1. Below the document table 3,
An optical scanning table consisting of a first mirror unit 7 equipped with a light source 5 and a first reflecting mirror 6 is provided so as to be movable linearly in the left-right direction of the drawing, and the optical path length between the document scanning point and the photoreceptor is kept constant. The second mirror unit 20 moves according to the speed of the first mirror unit, and the reflected light from the document table 3 passes through the lens 21 and the reflection mirror 8 onto the photosensitive drum 9 as an image carrier. The light enters in a slit shape. Around the drum 9, a corona charger 10,
A developing device 11, a transfer section 12, a separation section 13, and a cleaning section 14 are arranged, and the copy paper 18 fed from the paper feed box 15 via each paper feed roller 16, 17 is further processed after the toner image on the drum 9 is transferred. The image is fixed by the fixing unit 19 and then ejected to the tray 35. In the fixing section 19, a fixing operation is performed by passing the developed copy paper between a heating roller 23 having a built-in heater 22 and a pressure roller 24. However, photoreceptors with a-3i:H surfaces are susceptible to surface chemical stability, such as the effects of long-term exposure to the atmosphere or moisture, and the effects of chemical species generated by corona discharge. , has not been sufficiently investigated so far. For example, items that have been left for more than a month will be affected by moisture.
It is known that the receptor potential is significantly reduced. On the other hand, amorphous hydrogenated silicon carbide (hereinafter a-3iC:H
It is called. ), its manufacturing method and existence are 'Ph11
．． Mag, Vol. 35'' (1978), etc., and its characteristics include high heat resistance and surface hardness, and a high dark resistivity (1012
~1013 Ω-cm), and that the optical energy gap changes over a range of 1.6 to 2.8 eV depending on the amount of carbon. However, there is a drawback that the long wavelength sensitivity becomes poor due to the widening of the band gap due to the inclusion of carbon. An electrophotographic photoreceptor combining such a-3iC:H and a-3i:H has been proposed, for example, in Japanese Patent Application Laid-Open No. 127083/1983. According to this, a-3i:H
The layer is a charge generation (photoconductive) layer, and below this charge generation layer is a
-3iCsH layer is provided, the upper layer a-3i:H provides photosensitivity in a wide wavelength range, and the lower layer a-3iC:H forming a heterojunction with the a-3i:) layer reduces the charging potential. However, a-3i: HJii
dark decay cannot be sufficiently prevented, and the charging potential is still insufficient to be of practical use.
3i: The presence of the H layer results in poor chemical stability, mechanical strength, heat resistance, etc. On the other hand, JP-A-57-17952 discloses a-8i:
A first a-3iC:HN is formed as a surface modification layer on the charge generation layer made of H, and a second a-3iC:HN is formed on the back surface (support electrode side).
a-3iC:H layer is formed. In addition, as related to this known technology,
As seen in Japanese Patent No. 23543, an inclined i
i (a-3i 1-xCx : H), and in this gradient layer, X=0 on the a-3isH side, and a-3iC
: A photoreceptor in which X=0.5 on the H layer side is known. However, when the present inventor conducted a study on the above-mentioned known photoreceptor, it was found that the effect of providing the surface modification layer is not so pronounced, especially in continuous repeated use. That is, during continuous running of 200,000 to 300,000 times, the a-3iC layer on the surface is mechanically damaged after about 70,000 to 80,000 times, and this causes white streaks and white spots as image defects, resulting in poor rigidity. Not enough. Furthermore, light resistance fatigue occurs during repeated use, image blurring occurs, and the electrical and optical characteristics are not always stable, and the effects of the use environment (temperature, humidity) cannot be ignored. Furthermore, it is necessary to further improve the adhesion between the surface modified layer and the charge generation layer. C. Object of the Invention The object of the present invention is to provide excellent adhesion between the surface modification layer and the charge generation layer, resistance to mechanical damage, and excellent printing durability.
Stable image quality without image blurring is obtained, there is little optical fatigue during repeated use, the residual potential is low, and the characteristics are compatible with the usage environment (
The purpose of the present invention is to provide a photoreceptor that is stable regardless of temperature and humidity. 2. Structure of the invention and its effects, that is, the present invention provides a charge blocking layer made of amorphous hydrogenated and/or fluorinated silicon containing at least one of carbon atoms, nitrogen atoms, and oxygen atoms; a charge transport layer made of amorphous hydrogenated and/or fluorinated silicon containing carbon atoms and oxygen atoms; a charge generation layer made of amorphous hydrogenated and/or fluorinated silicon; an element of group Ma or group Va of the periodic table; an intermediate layer doped and consisting of amorphous hydrogenated and/or fluorinated silicon; a surface containing few (all one) of carbon, nitrogen and oxygen atoms and consisting of amorphous hydrogenated and/or fluorinated silicon; According to the present invention, since the surface modified layer contains at least one atom of carbon, nitrogen, and oxygen, it is resistant to mechanical damage. The present invention also uses an impurity-doped intermediate layer between the surface modification layer and the charge generation layer. This improves the adhesion between the surface modified layer and the charge generation layer.Also, since the surface modified layer and the intermediate layer are provided on the charge generation layer, in addition to the above, the adhesiveness between the surface modified layer and the charge generation layer is improved. It has been confirmed that it has excellent resistance to light fatigue during use, has no image blurring, has low residual potential, and has stable electrical and optical properties at all times and is unaffected by the environment in which it is used. The present invention will be described in detail with reference to embodiments. Fig. 1 shows an a-3t electrophotographic photoreceptor 39 for positive charging according to the present embodiment. This photoreceptor 39 has an A1
a-8i:) ((a-3i An N+ type heavy charge blocking layer 44 consisting of (C) (N) (0): a-3t:H (this is a-3i C
a charge transport layer 42 consisting of a
A charge generation layer (without impurity doping or made intrinsic) 43 made of 5t:H, and a charge generation layer 43 made of H, Group IV a or V of the periodic table.
Intermediate N46 consisting of P+ type or Gi type amorphous hydrogenated silicon heavily doped with group a elements, and
Amorphous hydrogenated silicon doped with a group A or group Va element to make it P-type, N-type, or intrinsic (without impurity doping) and containing at least one of N, C, and O. a-3i (C) (N)
(0): Represented as H. ) and a surface-modified layer 45 that is laminated. The charge generation layer 43 has a ratio of resistivity ρ in the dark to resistivity ρ during light irradiation that is sufficiently large as an electrophotographic photoreceptor, and has good photosensitivity (particularly to light in the visible and infrared regions). In addition, when the carbon atom content of each of the above layers is in the range of 0 to 70%, the optical energy gap (
Since there is an almost linear relationship with E g, opt),
It can be defined by replacing the carbon atom content with the optical energy gap. In addition, if the carbon atom content of a-3iC:H is appropriately selected, remarkable effects such as an increase in specific resistance and an improvement in charging potential holding ability can be obtained as shown by curve a in FIG. 3. That is, as shown by curve a in FIG. 3, when the carbon atom content is 30
When ~90% a-5iC:H is used, its resistivity varies according to the carbon content and is greater than or equal to 101 aΩ-0. The above tendency is that a-3iN containing N or O instead of carbon
The same applies to :H, a-3iO:H. The above layer 45 is essential for modifying the surface of the photoreceptor and making the a-3i photoreceptor practically superior. That is, it enables the basic operations of an electrophotographic photoreceptor, such as charge retention on the surface and attenuation of the surface potential due to light irradiation. Therefore, the repetitive characteristics of charging and optical attenuation become very stable, and good potential characteristics can be reproduced even if left for a long period of time (for example, one month or more). On the other hand, in the case of a photoreceptor having a-5t:H as a surface, it is easily affected by humidity, air, ozone atmosphere, etc., and the potential characteristics change significantly over time. In addition, since the layer 45 has a high surface hardness, it has abrasion resistance during processes such as development, transfer, and cleaning, and also has good heat resistance, so a process that applies heat such as adhesive transfer can be applied. . In order to comprehensively achieve the excellent effects described above, it is important to select the composition of the layer 45. That is, when containing carbon atoms, Si+C=100at
omic% (hereinafter, atomic% is simply expressed as %)
When 1%≦(C)690%, furthermore 10%≦(C
) 570% is desirable. Due to this C content, the above-mentioned resistivity becomes the desired value, and the optical energy gap becomes approximately 2.5 eV or more, and the irradiated light is a-3i due to the so-called optically transparent window effect for visible and infrared light. : It becomes easier to reach the H layer (charge generation layer) 43. However, if the C content is 1% or less, disadvantages such as mechanical damage occur, and the specific resistance tends to fall below the desired value (and a portion of the light is absorbed by the surface layer 45, reducing the photosensitivity of the photoreceptor. Furthermore, if the C content exceeds 90%, the amount of carbon in the layer increases, and semiconductor properties are likely to be lost, and a-
Since the deposition rate when forming a 3iC:H film by a glow discharge method tends to decrease, the C content is preferably 90% or less. Similarly, for a layer 45 containing nitrogen or oxygen, 1
%≦(N)690% (furthermore IO%s (N) 570
%) is good, 0%< (0) 570% (even 5%≦

[0]≦30%). In order to improve the charging ability, the surface modified layer 45 may have a high resistance. For this purpose, the surface modified layer may be made intrinsic. In positively or negatively charged use, in order to facilitate the injection of electrons or holes from the intermediate layer into the surface-modified layer and to minimize the residual potential, the surface-modified layer may be of P or N type. good. The amount of impurity doped in each case (at the time of glow discharge decomposition described later) may be as follows. Intrinsicization: P type: N type: PH3/SiH+ 1 to 1000 (preferably 5
0-500) Capacity Ppm (S i N O: H(F
). s i co: H (common to Fl) In addition, the layer 45 is a-3iCO, a-3iNO1a-3t
o, , a-3ioz, etc., and the film thickness is within the range of 400 people ≦ t ≦ 5000 people (especially 400 people ≦ t
It is also important to select ≦2000 people. That is, if the film thickness exceeds 5000, the residual potential VR becomes too high and the photosensitivity decreases, resulting in a-3
It is easy to lose the good characteristics as an i-type photoreceptor. Furthermore, if the film thickness is less than 400 mm, charges will no longer be charged on the surface due to the tunnel effect, resulting in increased dark decay and decreased photosensitivity. To enable this, the intermediate layer may be of P or N type. The doping amount for controlling the conductivity type may be the same as that for the surface modification layer. The thickness of this intermediate layer is preferably 50 to 5,000 people, but if it exceeds 5,000 people, the same phenomenon as described above is likely to occur, and if it is less than 50 people, the effect as an intermediate layer will be poor. Preferably, the thickness is 100 Å or more and 1000 Å or less. Regarding the charge generation IW 43, in order to improve the charging ability, the resistance of the charge generation layer may be increased. For this purpose, the charge generation layer may be made intrinsic. For this purpose, it is preferable to set the capacity to BzHs/SiH+=1 to 20 ppra. Further, the charge generation layer has a thickness of 1 to 10 μm, preferably 5 to 7 μm.
It is better to set it to m. If the charge generation 1it43 is less than 1 μm, the photosensitivity will not be sufficient, and if it exceeds 10 μm, the residual potential will increase, which is insufficient for practical use. Regarding charge transport [42], in order to optimize chargeability and sensitivity, it may be made intrinsic as necessary. The doping amount for making it intrinsic is (B2H6)/(SiH+
)=1 to 20 ppm by volume is optimal. However, since the above value depends on the C concentration, it is not necessarily limited to the above value. The thickness of the charge transport layer is preferably 10 to 308 m. In addition, the composition of the charge transport layer is 1% <[C]≦
30%, preferably 10%≦ (C) 530% is good, 0% [O] 610%, preferably 0% [0
]≦1% is good. In addition, the charge blocking layer 44 may be made of elements of Group Va of the periodic table (for example, phosphorus), if necessary, to sufficiently prevent hole injection from the substrate 41 and to improve sensitivity and charging ability.
is doped by glow discharge decomposition to make it intrinsic, and further to N-type (
Furthermore, it becomes a crawling type). The doping amount is controlled by the composition of the blocking layer as follows. a-3iC or a-3iCO: Intrinsic B2Hs/5iH42~20 capacity pp+aN type (N') PH3/S 1H41~1000 capacity ppma
-3iN or a-3iNO: Intrinsic B 2 Hs/S i H41~2000 ppm N type (N') P H3/S i H41~2
000 The blocking layer may be a compound such as SiO or 5iOz. Further, the thickness of the blocking layer 44 is preferably 500 μm to 2 μm. If it is less than 500, the blocking effect will be weak, and if it exceeds 2 μm, the charge transport ability will tend to deteriorate. The composition of the blocking layer 44 is preferably as follows. That is, 1%〈〔03590%, preferably 10%≦(C) 570%, and 1% [N359
0%, preferably 10% [N1570%, 0%
≦(0)570%, preferably 0%≦

It is preferable that [0]≦30%. Note that each of the above layers needs to contain hydrogen. In particular, the hydrogen content in the charge generation layer 43 is essential to compensate for dangling bonds and improve photoconductivity and charge retention, and is preferably 10 to 30%. This content range also applies to the surface modification layer 45, blocking layer 44, and charge transport layer 42. Further, as an impurity for controlling the conductivity type of the blocking layer 44, in addition to boron, Al, Ga, In
% 71 etc. can be used. In addition to phosphorus, Group Va elements of the periodic table, such as A s s S b, can be used for N-type formation. Next, a method for manufacturing the above-mentioned photoreceptor (for example, drum-shaped) and an apparatus therefor (glow discharge apparatus) will be explained with reference to FIG. A drum-shaped substrate 41 is set rotatably vertically in a vacuum chamber 52 of this device 51, and a heater 55 is used to rotate the substrate 41.
can be heated to a predetermined temperature from the inside. A cylindrical high frequency electrode 57 with a gas outlet 53 is disposed around and facing the substrate 41, and a glow discharge is generated between the electrode 57 and the substrate 41 by a high frequency power source 56. In addition, 62 in the figure is a supply source of SiH4 or a gaseous silicon compound, 63 is a supply source of hydrocarbon gas such as CH4, and 64 is a supply source of N2.
65 is a supply source of oxygen compound gas such as 02, 66 is a carrier gas supply source such as Ar,
67 is an impurity gas (for example, B2Hβ) supply source, and 68 is each flow meter. In this glow discharge device, first, the surface of a support, for example, an Al substrate 41, is cleaned and then placed in a vacuum chamber 52, so that the gas pressure in the vacuum chamber 52 is 1O-6.
Torr, and exhaust the air, and keep the substrate 41 at a predetermined temperature, particularly 100 to 350°C (preferably 150 to 350°C).
Heat and maintain at 300°C. Next, using a high-purity inert gas as a carrier gas, SiH4 or a gaseous silicon compound, CH4, N2.02, etc. are appropriately introduced into the vacuum chamber 52, and the high-frequency power source 56 is used under a reaction pressure of, for example, 0.01 to 1 QTorr. High frequency voltage (e.g. 13.56 MH
z) is applied. As a result, each of the above reaction gases is decomposed by glow discharge between the electrode 57 and the substrate 41, and the N+ type a-
3iC: HsA type a-3iCO: H% a S
i: H% P" or Nne a S s: H-. a-3iC:H above layer 44.42.43.46.4
5 in succession (i.e., corresponding to the example of FIG. 1, for example). In the above manufacturing method, the support temperature is set at 100 to 350°C in the step of forming the a-3i layer on the support, so the film quality (especially electrical properties) of the photoreceptor can be improved. . In addition, when forming each layer of the above a-3t photoreceptor,
In order to compensate for dangling bonds, fluorine is introduced in the form of siF, etc., in place of the above-mentioned H or in combination with H, and a Si:F%a-3i:H:
F, a-3iN:F,, a-3iN:H:F, a
-3iC:F, a-3iC:H:F can also be used. In this case, the fecal content is preferably 0.5 to 10%. The above manufacturing method is based on the glow discharge decomposition method, but there are also sputtering methods, ion blating methods, and methods in which Si is evaporated while introducing activated or ionized hydrogen in a hydrogen discharge tube. (In particular, Japanese Patent Application Laid-Open No. 56-78413 (Patent Application No. 54-152) filed by the present applicant)
The above photoreceptor can also be manufactured by the method of No. 455). Hereinafter, the present invention will be described with reference to specific examples. By glow discharge decomposition method, the first
An electrophotographic photoreceptor having the structure shown in the figure was manufactured. That is, first, after cleaning the surface of a support, for example, a drum-shaped Al substrate 41 having a smooth surface, it is placed in a vacuum chamber 52 shown in FIG.
Torr, and exhaust the air, and keep the substrate 41 at a predetermined temperature, particularly 100 to 350°C (preferably 150°C).
-300°C). Next, high-purity Ar gas was introduced as a carrier gas, high-frequency power with a frequency of 13.56 MHz was applied under a back pressure of 0.5 Torr, and preliminary discharge was performed for 10 minutes. Then, S i
A reaction gas consisting of H4 and PH3 was introduced, and the flow rate ratio was 1:
1: 1: (Ar+ of (1,5Xl0-3)
By glow discharge decomposition of SiH++CH+ or N2+PH3) mixed gas, N+W a-3iC:HIM44 and a-3iCO:H charge transport layer 42, which play a charge blocking function, are sequentially deposited to a predetermined thickness at a deposition rate of 6 μm/hr. A film was formed. Subsequently, the supply of BAH and CH4 was stopped, SiH4 was decomposed by discharge, and a-3 with a thickness of 5 μm was formed.
t:) (Layer 43 was formed.Subsequently, the flow rate ratio of impurity gas was changed to perform glow discharge decomposition, and the intermediate layer 46 whose film thickness was also changed was formed, and further B 2 Hs / S f
Further providing a-3iCO:H or a-3i No:H surface protection rN45 with H4 = 1009 ppm,
Completed an electrophotographic photoreceptor. As a comparative example, a photoreceptor without an intermediate layer was prepared. The structure of the photoreceptor thus produced was summarized as follows. (1) 1 surface modified layer: a-3iNO:H2N, ta-
3iCO:H (2), intermediate layer: doping amount, film thickness change (see Figure 5) (3), a-3i:H charge generation layer: film thickness -5
μm(4), a-3ico: H charge transport layer: Thickness = 15 μm C content = 12% 0 content = 1000100 0pp, a-3i C: H or a-3iN:H charge blocking layer: Thickness = 0 .5μm carbon content = 12
% (6), Support: AI! Cylinder (mirror polished finish)
Next, various tests were conducted using each of the photoreceptors described above as follows. 1 unit left hand strength As shown in Figure 6, 0,
A load W is applied to the 3R diamond needle 70, and the photoreceptor is moved by the motor 71.
Rotate it and make a wound. Next, the electrophotographic copying machine U-B
An image is produced using a modified machine ix1600 (manufactured by Konishiroku Photo Industry Co., Ltd.), and the scratch strength (g) of the photoreceptor is determined by the load at which a white streak appears on the image. After acclimatizing the photoconductor in a modified electrophotographic copying machine U-Bix 4500 (Konishiroku Photo Industry Co., Ltd.) for 24 hours in an environment with a temperature of 33°C and a relative humidity of 80%, the developer, paper, After 1000 copies were made without contact with the blade, an image was produced, and the degree of image blurring was determined based on the following criteria. ■=There is no image blurring at all, and the reproducibility of 5.5-point alphabetic characters and thin lines is good. 0: 5.5 point letters become slightly thicker. △: 5.5 point letters are crushed and difficult to read. X: 5.5 points of unreadable letters. By measuring the potential using a modified VFLv U-Bix 2500,
The surface potential of the photoreceptor that remains even after being irradiated with static eliminating light 301ux-see having a peak at 400 nm. Measured with a 360SX type electrometer (manufactured by Trek) using a 11-plate Eto Yue and a U-Bix 2500 modified machine (manufactured by Konishi Roku Photo Industry ■), with a photoconductor inflow current of 200 μA and no i-light. Surface potential just before development. ``'E' (lux = sec) Using the above device, sharply cut the long wavelength component of 620 nm or more of the image exposure wavelength using a gicroic mirror (manufactured by Kotai Kogaku Co., Ltd.), and change the surface potential from 500 V to 250 V. The amount of exposure required to reduce the amount of light by half. (The amount of exposure was measured using a 550-1 photometer (manufactured by EG and G). The results are summarized in Figure 7. From these results, it can be seen that It can be seen that if the body is prepared, a photoreceptor with excellent performance for electrophotography can be obtained.

[Brief explanation of the drawing]

1 to 7 show examples of the present invention, in which FIG. 1 is a sectional view of an a-3i photoreceptor, and FIG. 2 is an a-3i photoreceptor.
A graph showing the optical energy gear of iC, FIG. 3 is a graph showing the a-3iCO resistivity, FIG. 4 is a schematic cross-sectional view of the glow discharge device, and FIG. 5 is a table showing the layer structure of each photoreceptor. FIG. 6 is a schematic diagram of a scratch strength tester, and FIG. 7 is a table showing the characteristics of each photoreceptor. FIG. 8 is a schematic sectional view of a conventional electrophotographic copying machine. In addition, in the symbols shown in the drawings, 39...a-3i type photoreceptor 41...
...Support (substrate) 42 ...Charge transport layer 43 ...Charge generation layer 44 ...Charge blocking layer 45 ...
. . . Surface modified layer 46 . . . Intermediate layer.

Claims (1)

[Claims] 1. A charge blocking layer made of amorphous hydrogenated and/or fluorinated silicon containing at least one of carbon atoms, nitrogen atoms and oxygen atoms; amorphous hydrogenated and/or fluorinated silicon containing carbon atoms and oxygen atoms; a charge transport layer made of hydrogenated and/or fluorinated silicon; a charge generation layer made of amorphous hydrogenated and/or fluorinated silicon; and an intermediate layer doped with a Group IIIa or Va element of the periodic table and made of amorphous hydrogenated and/or fluorinated silicon. and a surface-modified layer containing at least one of carbon atoms, nitrogen atoms, and oxygen atoms and made of amorphous hydrogenated and/or fluorinated silicon, which are sequentially laminated.