Electrophotographic member with silicide interlayer

An electrophotographic photosensitive member comprising (a) a substrate made of an electrically conductive material, (b) a silicide layer formed on the surface of the substrate, and (c) a photoconductive layer superposed on the silicide layer being composed chiefly of amorphous silicon; which is usable for copying machines and intelligent copying machine.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an electrophotographic photosensitive 
member including a photoconductive layer which is composed chiefly of 
amorphous silicon. 
2. Description of the Prior Art 
Electrophotographic photosensitive members which are composed chiefly of 
amorphous silicon are disclosed, for example, in U.S. Pat. Nos. 4,394,426, 
4,359,514, 4,414,319, 4,418,132, 4,423,133, 4,771,042, etc. Such 
photosensitive members have various advantages over those composed chiefly 
of selenium or cadmium sulfide in that they have higher resistance to heat 
and abrasion, are harmless and have higher photosensitivity. Furthermore 
these members have the advantage that they are usable for copying machines 
and intelligent copying machines including a laser printer because of 
sufficient sensitivity to light of long wavelengths. 
When amorphous silicon is used for electrophotographic photosensitive 
members, the photoconductive layer formed on the substrate must have a 
sufficient thickness so as to have a high dark resistivity and to obtain 
the amount of charge required for the developing process. The 
photosensitive member has a surface layer for preventing the flow of 
surface charges from the surface of the member into the photoconductive 
layer. The surface layer is made of a material composed chiefly of 
amorphous silicon and containing nitrogen, carbon or oxygen. 
However, the photoconductive layer when it has sufficient thickness, tends 
to release or peel from the substrate so that the electrophotographic 
photosensitive member comprising the photoconductive layer has 
insufficient in its durability for use. Larger thickness of the 
photoconductive layer result in higher releasability or peelability. 
SUMMARY OF THE INVENTION 
The present invention provides an electrophotographic photosensitive member 
comprising: 
(a) a substrate made of an electrically conductive material, 
(b) a silicide layer formed on the surface of the substrate; and 
(c) a photoconductive layer superposed on the silicide layer being composed 
chiefly of amorphous silicon. 
The electrophotographic photosensitive member of the present invention may 
further include a blocking layer between the silicide layer and the 
photoconductive layer. Preferably the blocking layer is composed chiefly 
of amorphous silicon and contains a substance for blocking flow of 
carriers from the substrate into the photoconductive layer when combined 
with the amorphous silicon, the content of the substance being high toward 
the substrate and low toward the photoconductive layer. 
In an electrophotographic photosensitive member of the present invention, 
the photoconductive layer forms a high-strength bond with the substrate 
through the silicide layer so that the durability of the photosensitive 
member is remarkably improved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Substrate 
The substrate of the electrophotographic photo sensitive member of the 
invention can be one which is already known in the art. Thus, it is 
usually in the form of a drum or belt. It is usually made of an 
electrically conductive material such as aluminum or stainless steel. The 
substrate made of the conductive material may be coated with a substance 
having a greater work function, such as Au, Cr, Cu, Ni, Pd, Pt, W, Mo, Ag 
or Ti, by vacuum evaporation or plating. Although the substrate may of 
course be without any coating, it is then desired that the substrate have 
a surface polished, for example, to a roughness of up to 0.1 .mu.m and/or 
be made of a highly purified conductive material, so as to be free from 
surface defects due to the presence of impurities. 
Furthermore, the substrate may be a nonmetallic heat generating body of 
silicon carbide, boron oxide, aluminum nitride, alumina, boron nitride or 
the like which has a ground electrode. When such a substrate is used, the 
photosensitive member can be easily heated, for example, to 40.degree. to 
50.degree. C. when it is to be used. This serves to prevent flow of images 
due to the condensation of water vapor on the photosensitive member. 
Besides, an under-coating layer may be formed between the substrate and the 
blocking layer in order to strengthen adherence therebetween. 
The under-coating layer can be prepared from a source gas for forming 
amorphous silicon, in which when the substrate is aluminum, a little 
amount of alkyl aluminum compound such as (CH.sub.3).sub.3 Al, 
(CH.sub.3).sub.2 AlH, CH.sub.3 AlH.sub.3, (C.sub.2 H.sub.5).sub.3 Al, 
(C.sub.2 H.sub.5).sub.2 AlH, C.sub.2 H.sub.5 AlH.sub.2 or the like is 
added. The preferred alkyl aluminum compound is (CH.sub.3).sub.3 Al or 
(C.sub.2 H.sub.5).sub.3 Al. 
Silicide layer 
The silicide layer, which is characteristic of the present invention, is 
formed on the surface of the substrate. Examples of the silicides are Co, 
Mo or W silicide, among which Mo silicide and W silicide are preferred. 
The silicide layer has a thickness of suitably 10-10000 .ANG. and may be 
prepared by the method known in the art (see Examples). 
Photoconductive layer 
The photosensitive member of the present invention includes a 
photosensitive layer which is composed chiefly of amorphous silicon 
(hereinafter referred to as "a-Si"). The layer may be made chiefly of 
i-type a-Si, p-type a-Si (containing a Group III element added thereto) or 
n-type a-Si (incorporating a Group V element). The concentration of a 
Group III or V element is suitably 5.times.10.sup.15 to 5.times.10.sup.18 
atoms/cm.sup.3. The layer may be made of p-type a-Si at the substrate side 
thereof and n-type a-Si at the other side thereof adjacent the surface 
layer so as to have a high resistivity. Further in order to give a high 
resistivity to the layer, O, C, N or the like may be added to such a 
material. It is desirable to give the layer a resistivity of 10.sup.9 to 
10.sup.12 ohm-cm and therefore to add impurities so as to afford such a 
resistivity. The amount of O to be added to give the desired resistivity 
is 2.5.times.10.sup.19 to 1.5.times.10.sup.22 atoms/cm.sup.3. The 
corresponding amount of C or N is 5.times.10.sup.21 to 4.5.times.10.sup.22 
atoms/cm.sup.3. The layer may be formed from a-Si having added thereto as 
impurities a small amount of an organic compound which comprises a Group 
III element, such as [(CH.sub.3).sub.3 Al].sub.2, (C.sub.2 H 
(CH.sub.3).sub.3 Ga, (C.sub.2 H.sub.5).sub.3 Ga, (C.sub.2 H.sub.5).sub.3 
-In or the like. 
The preferred photoconductive layer is p-type a-Si layer, n-type a-Si layer 
or high-resistivity layer. The layer must have a thickness sufficient to 
obtain an amount of charges required for the developing process. More 
specifically, the layer is usually about 5 to about 80 .mu.m in thickness. 
Surface layer 
The surface layer is provided primarily to prevent the charges provided on 
the free surface of the photosensitive member from flowing into the 
photoconductive layer and impairing the initial charge characteristics of 
the member. For this purpose, the layer is preferably a highresistivity 
layer. The surface layer is composed chiefly of a-Si. To give a high 
resistivity to the layer, the a-Si has added thereto a substance which 
forms an insulating material when combined with the a-Si. 
A useful substance for forming the insulating material is carbon. The 
carbon sources are hydrocarbons which can be represented by C.sub.n 
H.sub.2n+2, C.sub.n H.sub.2n or C.sub.n H.sub.2n-2 where n is an integer, 
such as CH.sub.4, C.sub.2 H.sub.6, C.sub.3 H.sub.8, C.sub.2 H.sub.4, 
C.sub.3 H.sub.6, CH.sub.2 H.sub.2 or the like, and may be used in 
admixture thereof. The other carbon sources are organosilanes which can be 
represented by R.sub.4 Si, R.sub.3 SiH, R.sub.2 SiH.sub.2 or RSiH.sub.3 
where R is for example a lower alkyl such as methyl or ethyl. 
The content of the substance (i.e., carbon) based on the silicon atoms is 
suitably low toward the substrate and high toward its surface. More 
specifically, the content is desirably 0.01 to 30 atomic % toward the 
substrate and 1 to 51 atomic % toward its surface. The most desirable 
content is 10 to 20 atomic % toward the substrate and 30 to 50 atomic % 
toward its surface. The term "atomic %" means the number of atoms of the 
substance contained per 100 atoms of the silicon. Preferably the content 
gradually increases from the substrate side toward the surface side. When 
having a higher content at the surface side, the surface layer possesses 
enhanced ability to retain surface charges (in other words, to prevent 
flow of charges into the photoconductive layer) and increased surface 
strength. On the other hand, the lower content at the substrate side 
serves to minimize the reduction of the photosensitivity. 
The surface layer has a thickness of about 0.1 to about 20 .mu.m, suitably 
about 0.1 to about 5 .mu.m, preferably about 0.5 to about 1.5 .mu.m. This 
thickness is much larger than that of conventional surface layers which is 
about 30 to about 1000 .ANG., i.e. about 0.003 to about 0.1 .mu.m, so that 
the layer is easy to make. Accordingly the layer is unlikely to have 
variations in its thickness and is useful for giving uniform copy images. 
On the other hand, despite the large thickness, the carriers entering the 
surface layer are easily movable since the content of the 
insulation-forming substance is lower at one side thereof adjacent the 
photoconductive layer. Further, when the content is made to decrease from 
the free surface side of the surface layer toward the photoconductive 
layer, the carriers are movable with greater ease. 
The surface layer may have incorporated therein a small amount of Group III 
or V element or an organic compound containing Group III metal (see 
examples given for the photoconductive layer) as impurities. The amount is 
usually 10.sup.-6 to 10.sup.-3 atomic %. 
Blocking layer 
Preferably the photosensitive member of the present invention has a 
blocking layer between the substrate and the photoconductive layer. The 
blocking layer has the function of preventing flow of carriers from the 
substrate into the photoconductive layer when the photosensitive member is 
charged and permitting the carriers produced by electromagnetic 
irradiation (as with light) in the photoconductive layer and moving toward 
the substrate to flow into the substrate. The blocking layer can be 
prepared from a-Si to which boron or phosphorus is added. Usually B.sub.2 
H.sub.6 gas is used as the boron source, and PH.sub.3 gas as the 
phosphorus source. Boron or phosphorus combines with the a-Si, forming a 
material for preventing flow of carriers from the substrate into the 
photoconductive layer. The boron source is used for forming the carrier 
blocking material when the photosensitive member is to be charged 
positively, or the phosphorus source is used for the same purpose when the 
member is to be charged negatively. 
Besides, in addition to the above boron or phosphorus sources, may add a 
small amount of an organic compound having Group III element which can be 
represented by R.sub.3 H, R.sub.2 MH or RMH.sub.2 where R is for example a 
lower alkyl and M is B, Al, Ga, In or Tl, or an organic compound having 
Group V element which can be represented by R.sub.3 X, R.sub.2 XH or 
RXH.sub.2 where R is the same as above and X is N, P, As, Sb or B. 
In order to obtain insulation property, N.sub.2 O, NO, CO.sub.2, O.sub.2, 
NH.sub.3 or N.sub.2 may be added to the a-Si. 
We have found it preferable to make the content of the additive high toward 
the substrate and low toward the photoconductive layer. More specifically, 
the additive content based on the Si atoms is 10.sup.3 to 10.sup.5 atomic 
ppm toward the substrate and 10 to 10.sup.3 atomic ppm toward the 
photoconductive layer. Preferably the content has a gradient. The layer of 
the above structure facilitates movement of carriers which tend to flow 
toward the substrate while preventing carriers from moving from the 
substrate toward the photoconductive layer. This serves to preclude the 
reduction of the photosensitivity. 
The blocking layer is about 0.05 to about 1 .mu.m in thickness. 
The blocking layer can be a silicide layer of CoSi.sub.2, Pb.sub.2 Si, 
MoSi.sub.2, WSi.sub.2 or the like, or a hetero element layer of Cu.sub.2 
O, PbO, FeO, NiO, GaP, InP, GaAlAs or the like. 
According to the invention, the blocking layer, the photoconductive layer 
and the surface layer can be formed over the substrate by the CVD, PVD, 
spattering or like known process with use of a known apparatus. However, 
for forming the blocking layer over the substrate and the surface layer 
over the photoconductive layer, it is desirable to treat the substrate 
surface and the photoconductive layer surface with plasma in an Ar, 
H.sub.2, NH.sub.3 or like gas atmosphere to assure improved adhesion and 
to reduce electron traps at the interface. 
REFERENCE EXAMPLES I TO V AND COMATIVE EXAMPLES I TO IV 
A process for fabricating electrophotographic photosensitive members will 
be described with reference to the following examples. FIG. 1 shows a 
hollow cylindrical closed container 5 internally equipped with a hollow 
cylindrical electrode 6. An aluminum substrate 1 having a superfinished 
surface for making a photosensitive member is rotatably inserted into the 
electrode 6. 
(Formation of blocking layer) 
With the substrate 1 thus mounted in place, the interior of the container 5 
is evacuated to a vacuum of about 1.times.10.sup.-6 atm. by a rotary pump 
7 and a mechanical booster pump 8. The substrate is thereafter heated to 
200.degree. to 300.degree. C. by an unillustrated heater (inserted in the 
substrate 1) while being rotated at 10 r.p.m. Next, Ar gas and H.sub.2 are 
introduced into the closed container 5 at a flow rate of 200 c.c./min., 
and glow discharge is caused to occur across the electrode 6 and the 
substrate 1 for pre-treatment. Subsequently the gas mixture is evacuated 
from the container 5, into which B.sub.2 H.sub.6 gas is then admitted 
along with SiH.sub.4 gas and H.sub.2 gas which are bases, to maintain the 
container 5 at a gas pressure of 1.times.10.sup.-3 atm. The ratio of 
B.sub.2 H.sub.6 gas to SiH.sub.4 gas to be mixed therewith is controlled 
to a specified value by the corresponding mass flow controllers 10. 
However, the supply of B.sub.2 H.sub.6 is decreased gradually. In this 
state, high-frequency power having a frequency of 13.56 MHz is applied to 
the substrate by a radio-frequency source 9 to cause plasma discharge. In 
a given period of time, a blocking layer 2 is formed over the substrate 1. 
(Photoconductive layer) 
After removing the gas mixture from the closed container 5, a specified 
quantity of O.sub.2 gas is introduced into the container along with the 
above-mentioned gases, followed by the same discharge as above, whereby a 
photoconductive layer 3 is formed over the blocking layer 2. 
(Formation of surface layer) 
The gas mixture is then removed from the closed container 5, into which 
SiH.sub.4 gas, H.sub.2 gas and CH.sub.4 gas are thereafter introduced in a 
specified ratio to cause discharge. CH.sub.4 gas is supplied at a rate 
gradually increasing with time as controlled by the corresponding mass 
flow controller 10, whereby a surface layer 4 is formed. 
The actual flow ratio of pure CH.sub.4 gas to pure SiH.sub.4 gas (CH.sub.4 
/SiH.sub.4) is 0.01-2.0, preferably 0.2-1.0 for a part toward the 
substrate and 0.1-10, preferably 0.4-6.0 for a part toward free-surface. 
In this way, a photosensitive member is obtained which has the structure 
shown in FIG. 2. In Reference Examples I to IX and Comparative Examples I 
to IV, photosensitive members were prepared by the above process under 
varying conditions as listed in Table 1. 
The surface layer of the members in Comparative Examples III and IV is 
formed by the addition of oxygen source instead of carbon source for 
giving insulating property. 
TABLE 1 
__________________________________________________________________________ 
SiH.sub.4 
B.sub.2 H.sub.6 /SiH.sub.4 Thickness of 
Layer (cc/min) 
(ppm) O.sub.2 /SiH.sub.4 
H.sub.2 /SiH.sub.4 
CH.sub.4 /SiH.sub.4 
N.sub.2 O/SiH.sub.4 
layer 
__________________________________________________________________________ 
(.mu.m) 
Reference 
Example 
I Blocking layer 
Start 
100 5000 0 1.0 0 0 1.0 
End 
100 500 0 1.0 0 0 
Photoconductive 
layer 
300 10 0.02 0.2 0 0 14 
Surface layer 
Start 
100 0 0 1.0 0.5 0 1.0 
End 
50 0 0 2.0 4.0 0 
II Blocking layer 
Start 
100 5000 0 1.0 0 0 1.0 
End 
100 500 0 1.0 0 0 
Photoconductive 
layer 
300 10 0.02 0.2 0 0 14 
Surface layer 
Start 
100 0 0 2.0 0.5 0 1.0 
End 
35 0 0 4.0 5.0 0 
III Blocking layer 
Start 
100 5000 0 1.0 0 0 1.0 
End 
100 500 0 1.0 0 0 
Photoconductive 
layer 
300 1 0.003 
0.2 0 0 14 
Surface layer 
Start 
100 0 0 2.0 0.8 0 0.5 
End 
50 0 0 4.0 4.0 0 
IV Blocking layer 
Start 
100 5000 0 1.0 0 0 1.0 
End 
100 500 0 1.0 0 0 
Photoconductive 
layer 
300 10 0.02 0.2 0 0 14 
Surface layer 
Start 
100 10 0 2.0 0.2 0 1.0 
End 
50 10 0 4.0 2.0 0 
V Blocking layer 
Start 
100 2000 0 1.0 0 0 1.0 
End 
100 2000 0 1.0 0 0 
Photoconductive 
layer 
300 20 0.02 0.2 0 0 14 
Surface layer 
Start 
100 0 0 1.0 0.5 0 1.0 
End 
50 0 0 4.0 4.0 0 
VI Blocking layer 
Start 
100 5000 0 1.0 0 0 1.0 
End 
100 500 0 1.0 0 0 
Photoconductive 
I 300 10 0.02 0.2 0 0 12 
layer II 300 0 0 0.2 0 0 2 
III 
300 10 0.02 0.2 0 0 0.1 
Surface layer 
Start 
100 0 0 1.0 0.5 0 1.0 
End 
35 0 0 2.0 4.0 0 
VII Blocking layer 
Start 
100 5000 0 1.0 0.1 0 0.5 
End 
100 500 0 1.0 0.1 0 
Photoconductive 
layer 
300 10 0.02 0.2 0.05 0 14 
Surface layer 
Start 
100 0 0 1.0 0.8 0 0.5 
End 
50 0 0 4.0 4.0 0 
VIII Blocking layer 
Start 
100 5000 0 1.0 0 0.02 1.0 
End 
100 500 0 1.0 0 0.02 
Photoconductive 
layer 
300 1 0.003 
0.2 0 0 14 
Surface layer 
Start 
100 10 0 1.0 0.4 0 0.5 
End 
50 10 0 4.0 4.0 0 
IX Blocking layer 
Start 
100 2000 0 1.0 0 0 1.0 
End 
100 2000 0 1.0 0 0 
Photoconductive 
layer 
300 10 0.02 0.2 0 0 14 
Surface layer 
Start 
100 0 0 1.0 0.1 0 0.5 
End 
50 0 0 4.0 0.4 0 
Example 
Comp. Ex. 
Photoconductive 
layer 
300 10 0.02 0.2 0 0 15 
Comp. Ex. 
Blocking layer 
100 2000 0 1.0 0 0 1.0 
II Photoconductive 
layer 
300 10 0.02 0.2 0 0 14 
Surface layer 
50 0 0 2.0 2.0 0 0.5 
Comp. Ex. 
Blocking layer 
100 2000 0 1.0 0 0 1.0 
III Photoconductive 
layer 
300 10 0.02 0.2 0 0 22 
Surface layer 
100 0 0.2 0.1 0 0 1.0 
Comp. Ex. 
Blocking layer 
100 2000 0 1.0 0 0 1.0 
IV Photoconductive 
layer 
300 10 0.02 0.2 0 0 18 
Surface layer 
Start 
100 0 0.2 1.0 0 0 1.0 
End 
50 0 0.6 0.2 0 0 
__________________________________________________________________________ 
The photosensitive members (drums) obtained were tested for the evaluation 
of performance. 
(Test methods) 
(i) Variations in the amount of charge 
The photosensitive drum is subjected to corona discharge under specified 
conditions, and the surface potentional (amount of charge) on the drum is 
measured by a surface potentiometer (TREK MODEL 344). The variations in 
the potential values along the length of the drum are expressed in 
percentage, with the mean value taken as 1. 
(ii) Copying test 
The photosensitive drum is installed in a copying machine and used for 
making copies to check the number of copies that can be produced without 
blur of images. 
(iii) Temperature-humidity cycle test 
The photosensitive drum is subjected to temperature-humidity cycles under 
conditions involving an upper limit of 70.degree. C. and 90%, and a lower 
limit of -10.degree. C. and the highest possible humidity that can be 
maintained. The time taken for one cycle is 1 hour for the upper limit, 2 
hours for the change from upper limit to lower limit, 1 hour for the lower 
limit and 2 hours for the change from lower limit to upper limit, i.e. 6 
hours in total. The drum is thus subjected to temperature-humidity cycles 
for 1000 hours, then heated in a constant-temperature chamber at 
80.degree. C. for 30 minutes and thereby conditioned uniformly for 
measurement, and thereafter checked for characteristics. 
The results are shown in Table 2, which also indicates the energy band 
diagrams obtained for Reference Examples I to VIII. 
TABLE 2 
______________________________________ 
Reference 
Variations in 
Copying test 
Temp.- Energy 
Example amount of (No. of blur- 
humidity 
band 
No. charge less copies) 
cycle test 
diagram 
______________________________________ 
I Within .+-. 5% 
200,000 Good FIG. 3 
II Within .+-. 5% 
200,000 Good FIG. 4 
III Within .+-. 10% 
50,000 Good FIG. 5 
IV Within .+-. 5% 
50,000 Good FIG. 6 
V Within .+-. 5% 
100,000 Good FIG. 7 
VI Within .+-. 5% 
100,000 Good FIG. 8 
VII Within .+-. 5% 
100,000 Good FIG. 9 
VIII Within .+-. 5% 
100,000 Good FIG. 10 
IV Within .+-. 5% 
100,000 Good FIG. 11 
Comp. Ex. 
Within .+-. 5% 
5,000 Poor -- 
I* 
Comp. Ex. 
At least .+-. 20% 
50,000 Good -- 
II** 
Comp. Ex. 
At least .+-. 20% 
10,000 Poor -- 
III 
Comp. Ex. 
At least .+-. 20% 
20,000 Poor -- 
IV 
______________________________________ 
Note 
*Single-layer drum. 
**Conventional threelayer drum. 
In FIGS. 3 to 11 and 12 to 14, plotted as ordinate are energy levels in the 
case of positive charging. Indicated as E.sub.C is the conduction band, at 
E.sub.F the Fermi band, and at E.sub.V the valence band. The region 
indicated at 1 corresponds to the substrate, at 2 the blocking layer, at 3 
the photoconductive layer, and at 4 the surface layer. In FIG. 3, the 
energy differences between E.sub.V and E.sub.F of between E.sub.V and 
E.sub.C are 0.2 eV for a, 1.75 eV for b, 0.3 eV for c, 1.8 eV for d, 2.4 
eV for e, and 4.0 eV for f. 
Thus, the photosensitive members of Reference Examples I to IX are 
chargeable with reduced variations in the amount of charge and found to 
have outstanding characteristics by the copying test and 
temperature-humidity cycle test. 
Further, the photosensitive members of Comparative Examples III and IV 
wherein oxygen is incorporated in the surface layer in place of carbon are 
inferior to the members of Reference Examples I to IX, especially in the 
useful life of the member. 
REFERENCE EXAMPLE X 
A blocking layer and a photoconductive layer were formed over a substrate 
under the same conditions as in Reference Example I, and a surface layer 
was thereafter formed at stepwise varying CH.sub.4 /SiH.sub.4 ratios as 
given below, whereby a photosensitive member was obtained. The H.sub.2 
/SiH.sub.4 ratio was the same as in Reference Example I. 
______________________________________ 
Reaction time CH.sub.4 SiH.sub.4 
______________________________________ 
Initial period (6 min.) 
0.2 
Intermediate period (6 min.) 
2.8 
Final Period (8 min.) 
4.0 
______________________________________ 
FIG. 12 is the energy band diagram of the photosensitive member thus 
obtained. The stepwise gradient pattern of CH.sub.4 /SiH.sub.4 ratio was 
found to correspond to the energy level pattern of the surface layer. 
The photosensitive member exhibited the same performance as the member 
obtained in Reference Example I. 
REFERENCE EXAMPLE XI 
A photosensitive member was prepared in the same manner as in Reference 
Example IX except that the gradient of CH.sub.4 /SiH.sub.4 ratio was made 
to have an arcuate pattern. FIG. 13 is the energy band diagram of this 
member. The member exhibited the same performance as the one prepared in 
Reference Example I. 
REFERENCE EXAMPLE XII 
A photosensitive member was prepared in the same manner as in Reference 
Example IX with the exception of varying the CH.sub.4 /SiH.sub.4 as listed 
below. 
______________________________________ 
Reaction time CH.sub.4 /SiH.sub.4 
______________________________________ 
Initial period (6 min.) 0.2 
Intermediate period I (3 min.) 
0.2 .fwdarw. 0 
Intermediate period II (3 min.) 
0 .fwdarw. 0.2 
Final period (8 min.) 0.2 .fwdarw. 2.8 
______________________________________ 
FIG. 14 is the energy band diagram of the member thus obtained. The member 
exhibited the same performance as the one prepared in Reference Example I. 
REFERENCE EXAMPLE XIII 
A blocking layer and a photoconductive layer were formed under the same 
conditions as in Reference Example I, and a surface layer was thereafter 
formed under the same conditions as in Reference Example I with the 
exception of additionally using B.sub.2 H.sub.6 gas in an amount of 100 
ppm based on the SiH.sub.4 gas, whereby diminished dark decay was 
realized. This effect appears attributable to the presence of the small 
amount of boron acting to render the surface layer more intrinsic. 
REFERENCE EXAMPLE XIV 
A blocking layer and a photoconductive layer were formed under the same 
conditions as in Reference Example I, and a surface layer was thereafter 
formed under the same conditions as in Reference Example I except that the 
gas obtained by evaporating (CH.sub.3).sub.3 Ga by the liquid bubbling 
method with use of H.sub.2 as a carrier gas was additionally used in an 
amount of 1% based on the SiH.sub.4 gas, whereby dark decay was 
diminished. This effect appears attributable to the presence of Ga acting 
as p-type silicon to render the surface layer more intrinsic. 
REFERENCE EXAMPLE XV 
A photosensitive member was prepared under the same conditions as in 
Reference Example I except that the photoconductive layer was formed 
without using B.sub.2 H.sub.6 gas but using the gas obtained by 
evaporating (CH.sub.3).sub.3 Ga by the liquid bubbling method with use of 
H.sub.2 as a carrier gas, in an amount of 0.2% based on the SiH.sub.4 gas. 
Consequently diminished dark decay was realized. This effect appears 
attributable to the present of Ga acting as p-type silicon to render the 
photoconductive layer more intrinsic. 
REFERENCE EXAMPLE XVI 
A photoconductive layer and a surface layer were formed over a substrate 
under the same conditions as in Reference Example I. The substrate was a 
hollow aluminum cylinder coated with chromium by electron beam vacuum 
evaporation. Although having no blocking layer, the photosensitive member 
obtained was comparable to the one prepared in Reference Example V in 
respect of photoconductive characteristics and durability. 
EXAMPLE I 
A hollow stainless steel cylinder was coated with W by electron beam vacuum 
evaporation to obtain a substrate, which was further coated with an 
amorphous silicon film having a thickness of hundreds of angstroms. The 
surface of the substrate was then heated by a YAG laser to convert the 
silicon to W silicide. A photoconductive layer and a surface layer were 
thereafter formed over the substrate under the same conditions as in 
Reference Example I. 
The photoconductive layer was formed with greater bond strength than when 
an amorphous silicon layer is formed directly over stainless steel. 
EXAMPLE II 
A hollow stainless steel cylinder was coated with Mo by electron beam 
vacuum evaporation to obtain a substrate. Si ions were injected into the 
substrate which was heated at 400.degree. C., followed by ion beam mixing 
to form Mo silicide. A photoconductive layer and a surface layer were 
thereafter formed over the substrate under the same conditions as in 
Reference Example I. 
The photoconductive layer was formed with greater bond strength than when 
an amorphous silicon layer is formed directly over stainless steel. 
[Test] 
The following tests were conducted for the evaluation of performance of the 
photosensitive members having a silicide layer as obtained in Examples I 
and II. 
(i) Adhesion Test 
Silicide layer was each formed on aluminum plates in various thickness by 
the method as described in Example I, and then the amorphous silicon layer 
having a thickness of 5 82 m was formed thereon to obtain samples of this 
invention. 
For comparison's sake, a sample was prepared which was directly formed on 
an aluminum plate the amorphous silicon layer of 5 .mu.m in thickness. 
Adhesive strength between the aluminum plate and the amorphous silicon 
layer was measured for each of samples according to the methods defined in 
JIS K 6856 "Testing methods for flexural strength of adhesives". The 
results are shown in Table 3. 
TABLE 3 
______________________________________ 
Thickness of Mo Silicide 
Adhesive strength 
layer (.ANG.) (Kg/mm.sup.2) 
______________________________________ 
0 5 
500 20 
1000 35 
5000 65 
8000 70 
10000 71 
______________________________________ 
(ii) Copying test and Temperature-humidity cycle test 
Two kinds of photosensitive drums A and B were prepared. 
Photosensitive drum A was prepared by forming over a hollow stainless steel 
cylinder W silicide layer of 1000 .ANG. in thickness as described in 
Example I and forming a photoconductive layer and a surface layer on the 
silicide layer under the same conditions as in Reference Example I. 
Photosensitive drum B was prepared by forming over the cylinder Mo silicide 
layer of 1000 .ANG. in thickness as described in Example II and forming a 
photoconductive layer and a surface layer on the silicide layer as in 
Reference Example I. 
For comparison, a drum was prepared which was directly formed on the 
cylinder a photoconductive layer and a surface layer (Comparison drum). 
Each of the drums was subjected to copying test and temperature-humidity 
cycle test as aforementioned. The results are shown in Table 4. 
TABLE 4 
______________________________________ 
Copying test 
(Number of blurless 
Temperature-humidity 
copies) cycle test 
______________________________________ 
Drum A &gt;100000 Good 
Drum B &gt;100000 Good 
Comparison 
5000 Poor* 
Drum 
______________________________________ 
*A part of the photoconductive layer peeled from the cylinder. 
REFERENCE EXAMPLE XVII 
A photosensitive member was prepared under the same conditions as in 
Reference Example I except that the substrate used was made of a 
nonmetallic heat generating material, i.e. silicon carbide, and lined with 
a metal (e.g. Al) coating. 
The member was usable without blur of images that could result from 
condensation of water vapor, when it was heated to 40.degree. to 
50.degree. C. with application of low voltage. 
REFERENCE EXAMPLE XVIII 
A photosensitive member was prepared under the same conditions as in 
Reference Example I except that the substrate used was a hollow cylinder 
of aluminum having a high purity of at least 99.9% (A1090 according to 
JIS). 
Because the substrate was made of high-purity aluminum and was freer from 
surface defects due to impurities (Fe, Cu, Si, Mn, Mg, etc.) in the 
aluminum, the amorphous silicon layers were formed with a reduced number 
of pinholes. 
EXAMPLE III 
A molybdenum silicide film was formed over a substrate by a radio-frequency 
spattering, using a target having an Mo/Si area ratio of 0.3 and heating 
the substrate at 200.degree. C. A photoconductive layer and a surface 
layer were thereafter formed under the same conditions as in 
REFERENCE EXAMPLE I. 
The photosensitive member obtained had high bond strength and good 
durability although slightly inferior to those of other example in 
blocking effect. 
REFERENCE EXAMPLE XVI 
The surface of a hollow copper cylinder was subjected to thermal oxidation 
or oxygen plasma treatment to form a copper oxide film over the substrate 
surface. A photoconductive layer and a surface layer were thereafter 
formed under the same conditions as in Reference Example I. Although 
having no blocking layer of amorphous silicon, the photosensitive member 
obtained had satisfactory blocking characteristics in addition to the 
advantages afforded by the present invention, owing to the presence of a 
hetero barrier between the copper oxide and the photoconductive layer. 
REFERENCE EXAMPLE XX 
A GaP film was formed over a substrate by a plasma reaction in a gas 
mixture of (CH.sub.3).sub.3 Ga, P vapor and (CH.sub.3).sub.2 Zn A 
photoconductive layer and a surface layer were thereafter formed under the 
same conditions as in Reference Example I. The photosensitive member 
obtained had satisfactory blocking characteristics in addition to the 
advantages afforded by the present invention, owing to a hetero barrier 
present between the GaP and the photosensitive member. 
REFERENCE EXAMPLE XXI 
A blocking layer and a photoconductive layer were formed over a substrate 
under the same conditions as in Reference Example I, and the surface of 
the resulting amorphous silicon layer was treated with plasma in NH.sub.3 
gas. Without any interruption, a surface layer was thereafter formed under 
the same conditions as in Reference Example I. 
The photosensitive member obtained exhibited improved photosensitivity and 
a reduction in residual potential. These effects appear attributable to 
the plasma treatment in NH.sub.3 resulting in diminished electron traps 
between the surface layer and the photoconductive layer.